1. No fourth quick since 1999. Until then their record was fine.
2. Not enough tall quicks.
3. Too much spin bowled.
This is so wrong that I actually am doubting if you really follow cricket or not. Don't you think that before putting any logic, you should back track the results to justify the hypothesis, if it fits the argument or not? Or, do you take a chance that no one would bother to cross check?
Here is the myth buster - why your logic won't satisfy someone like me: PAK has won 4 Tests in AUS - 1977 at SCG, 1979 at MCG, 1981 at MCG & 1996 at SCG. These are PAK's bowling combination and share of overs
1. SCG '77 (8 balls over): Total overs bowled: 64 + 42 = 106.
Imran: 26 + 20 = 46 overs, 12 wickets
Sarfraz: 16 + 15 = 31 overs, 6 wickets
Qasim: 4 + 2 = 6 overs, 0 wickets
Asif Iqbal: 15 + 0 = 15 overs, 0 wickets
Mushtaq Mo.: 2 + 0 = 2 overs, 0 wickets
Javed: 1 + 5 = 6 overs, 1 wicket
Basically, PAK went with TWO pacers and 18 wickets were taken by them, 1 run-out
1979 MCG (Packer compromised AUS) (8 balls overs): Total overs bowled: 62 + 92 = 154 overs
Imran: 18 + 27 = 45 overs, 4 wickets
Sarfraz: 23 + 35 = 58 overs, 11 wickets
Sikandar: 10 + 7 = 17 overs, 0 wickets
Mushtaq Mo.: 7 + 11 = 18 overs, 0 wickets
Wasim Raja: 5 + 3 = 8 overs, 2 wickets
Mazid: 0 + 9 = 9 overs, 0 wickets
PAK went with 3 pacers and 3rd one bowled less that the spin all-rounder. Two main pacers took 15 of the 17 wickets to bowlers, 3 run-out.
1981 MCG: Total overs bowled: 134 + 72 = 206 overs
Imarn: 24 + 14 = 38 overs, 5 wickets
Sarfraz: 14 + 15 = 29 overs, 5 wickets
Sikandar: 2 + 0 = 2 overs, 0 wickets
Qasim: 55 + 24 = 79 overs, 7 wickets
Wasim Raja: 37 +13 = 50 overs, 1 wicket
Majid: 2 + 4 = 6 overs, 0 wicket
Javed: 0 + 2 = 2 overs, 0 wickets.
Again, basically 2 pacers and third one was injured after 2 overs. Two spinners bowled 129 of 206 overs
1996 SCG: Total overs bowled - 98 + 66 = 164 overs
Wasim: 24 + 16 = 40 overs, 6 wickets
Waquar: 11 + 6 = 17 overs, 3 wickets
Mushi: 36 + 30 = 66 overs, 9 wickets
Saqlin: 22 + 13 = 35 overs, 2 wickets
Sohail: 5 + 1 = 6 overs, 0 wickets.
PAK went with 2 +2 combination and also used Sohail's spin.
So, your first logic doesn't stand at all - PAK never won a Test with 4 pacers (I actually am not sure if they had ever played any with 4 pacers - MCG 1990 may be). In fact, two of the four Tests were won with two pacers & two spinners combination, and the MCG 1981 Test which was won by innings had 2 overs from 3rd seemer.
Your second logic again doesn't stand much, because of the pacers used in these Tests, Sarfraz was probably 6'4", Wasim 6'3", Imran around 6'1". Both Sikandar and Waquar below 6' and rest were spinners. However, in general tall pacers will get extra advantage, anywhere particularly in Australia - BUT, they have to have skills first - just for the height pacers like Ehsan Adil won't survive there. There are many short fast bowlers that have won Tests, even series in AUS - Larwood, Marshall, Styen, Frank Tyson were under 6', Australia's own Lindwall & Ryan Haris were under 6' and DK Lille was bang on 183cm (6'0"). Didn't win a Series there, but 5'11" Kapil is among the best pacers in AUS in Test cricket's history.
Number three is your biggest hoax in this logic - PAK won two Tests of the four when genuine quality spinners bowled many, many tight overs and kept one end dried, so that Captain could rotate his two front line pacers. In 1977 & 79, it was an inhumane effort by Imran & Sarfraz that they kept bowling relentlessly overs after overs - particularly Sarfraz, he was past 30 in 1979 (that too officially) & yet bowled tirelessly for 58, 8 balls overs in a span of 3.5 days - including no balls, he bowled 80+, 6 ball overs in 11 sessions and took 11 wickets ... these days entire PAK Pace battery will be required to be carried on stretchers, if they are to bowl 80 overs in 3 days together.
I am sorry not to even consider any of your logics here - even the height issue, which is a hygiene factor.
Here are my takes - PAK has been pathetic in AUS since 1999, because of -
1. It's poor batting under pressure - even of absolute belters, whenever pressure had been applied batting collapsed (It was the case in past as well, but not hopelessly like this). Past PAK batting was County tempered, they could fight it out mentally. After Imran blew AUS in first day at SCG 1977, DK Lille and his team threw absolutely everything to PAK batsmen on Day 2 - filthy mouth, intermediating, sledging, body contact ..... the guys who stood firm were Asif Iqbal (120) & two young guys - Javed (64), Haroon (57) - Javed was not yet 20 then (Officially), and he asked Lille to shut up his "****ing mouth" and try to bowl better so that he could get Javed out - something DK never forgot, eventually it busted at WACA 1981 - these were men, you know. Put these current lot against old filthy mouth Aussies, you'll smell bad in their trousers.....
2. AUS is a team that never picks posedu all-rounders to fill up bowling quota - if it's an all-rounder, it has to be some class - Giffen, Noble, Gregory, Lindwall, Miller, Benaud, Davidson, Gilmore ...... indeed a class of their own. Otherwise, AUS produces the likes of Faheem Ashraf & Shadab Khan in dozens - THIS MEANS, while batting, you'll never get "perfume" overs from AUS - 4 out & out wicket taking bowlers, always at you relentlessly, no where to hide. Unless you are mentally tough, technically sound and extremely confident to fight it out - you won't score many in AUS even on absolute belters.
3. Negative Captaincy - AUS is not a place for faint hearts. If you play cricket there to avoid defeat, you are dead before the start, they'll eat you alive. No wonder the 4 wins that PAK had were under Mushtaq, Mushtaq, Imran & Wasim. Since 1999, PAK has been led in AUS by MoYo, Misbah & Azhar (Inzi led only one at WACA in 2004) - to say politely, absolute cowards, who would play safety first cricket and give initiatives back to AUS. Even against that frightening AUS, Shoaib bowled his heart out to be let down by his batsmen and Captain. Also, AUS is a place where scoring rate in Test match matters - you have to score quickly when the bowlers are down - I have seen PAK batting almost stagnated after a good start eventually suffering collapse - this actually will go against Captain, not enough encouragement to play natural game and take shots when due.
4. AUS is a place where you'll need to hold on to your catches - overs 70% dismissals happen there via catch and most behind batsman. PAK, being an atrocious catching side in AUS (& SAF) have dropped their way to few Tests from winning position. In AUS, first thing you need is a Wicket Keeper, not Goal Keeper and in those four wins, WKs were Bari, Bari, Bari & Latif (Moin dropped about 12 in first two Tests of that series).... for a reason.
5.
And this one is the most crucial one - height, no height, spin or pace ... nothing will work unless you have the quality. Number doesn't matter here - you can pick six, 6'6" pacer in AUS, if they are Ehsan Adil class, Aussies will score at 4+.... I have mentioned Ehsan Adil few times here - not to downplay the guy, but for a reason, you may know. In last 20+ years, more precisely since English Counties have stopped hiring PAK players in bulk, the Test bowling quality has gone down significantly - in AUS, you need much better bowling plan and execution for a touring bowler because the sweet length there is unique, different from anywhere, may be bar SAF partially. PAK has been poorest in that regard over last 2 decades - pacers have wasted new ball by loosing radar for too much focus on speed gun, then failed with old ball for attempt to non-existent reverse, spinners have bowled flat-out darts with defensive field.
Bottom line is - AUS in AUS is the toughest place on earth to play cricket against, every team will struggle to match them there even at their peak. Over last 23 years, PAK lacked the skill, quality, quantity, courage & intelligence to compete with them in any aspect of the game. If it was 80s, PAK could have got away with few draws, but ICC is at fault here - they have closed the back doors to steal a draw by ensuring 450 overs per Tests .... and it doesn't rain much in Test seasons in AUS .... hence 14-0 and it'll continue for foreseeable future.