These days, task of Umpire is becoming more & more difficult because of the DRS & so many camera used to expose them. This BD-ENG series was played on a difficult wicket with turn, uneven bounce & double paced surface, where always something was happening. Also, out of 80 wickets, more than half required tough umpiring calls. Normally, it's tougher to Umpire on deteriorating wickets in a Test, because Umpires get confused on how much the ball is going to turn & bounce from previous day.
I actually feel sorry for Dharma because luck also went against him on marginal calls. Take his last 2 over rules - Stokes was plumb LBW & he reviewed it just for the sake of it, eventually it was found that the ball had touched may be less than 1 mm of his gloves. This was similar case in 1st Test for Moeen. Last innings, Cook was given LBW & everyone would have accepted that - not sure how it showed missing in DRS. And, I can go with few others as well - like the LBW of Balance which wasn't given (1st Test) - only a DRS review showed that the ball hit pad probably 0.1 second early. In olden days, sometimes players also helped umpires by walking or not claiming catches that they knew off pad or had grassed. These days gamesmanship has gone to ugly level & I do believe time for ICC to bring something like "Yellow card for diving" in football. May be, we can introduce demerit points after every match for too much appeal or faking inside edges.
I actually think, Umpiring standard is not that bad, actually better - it's too much advanced technology, that is exposing them. For example, Umpires like Frank Chester, Dickey Bird or Shepard are considered like saints, but they made lots of mistakes as well. These days, despite sniko & ball tracking, I am sure overall correct decision is close to 90% - use same technology 35/85 years back, many of the greats would have been badly exposed. The missed "No Ball" by Rifel looks silly, but PAK won a Test at Old Traford, because Shepard (Or Nichols?) missed few over stepping that got wickets - now days batsmen would have been called back, & we would have made laugh of the Umpire.
Personally, I think, the main issue is DRS - it should never be with players. Umpire will take his own decision - if he is confused/not sure - he'll call 3rd Umpire/Match Referee for a closer look & give him feedback - after that, once decision given that's the end of it - no more analysis. In olden days, the golden rule was - " A batsman is OUT, not because he was actually out, rather he was judged out by the Umpire, as per the laws of Cricket" - it still applies. Giving DRS to players doesn't serve justice - Mushi missed one review & decided not to review Moeen's case; same Moeen decided not to review on 3rd morning of 2nd Test for same reason. But, if we make DRS unlimited, then not only WI, every team will bowl 83 overs in 6.5 hours. The 3rd option (not losing a review for "marginal decision") is also extremely time consuming - about 90% calls are marginal (which means, Review will not be lost), therefore teams 'll review almost every chancy calls & even after 15-20 reviews, they might have one more to try.
DRS was introduced to eradicate Umpiring howlers - unfortunately it's been used as a chance to survive or get a wicket. And, that is making Umpires scared to take bold decisions. Dharma gave an excellent decision of giving Tamim out (On 101), without offering shot - now, less than half a CM on impact point or hitting point (stamp), it would have looked silly. Similarly, he judged Taijul Not Out, Stokes took a chance & the decision was turned probably for a millimeter in it. Without DRS at players hand, hardly any of those incidences I mentioned here would have been any issue. Most of those would have been stayed as it is - may be Umpires would have consulted with 3rd Umpire for Balance's call, Moeen's call (1st Test), Taijul's call before giving it.
I do study the game in open mind & I can tell that every elite Umpire these days would have been among top 2/3 Umpires in 20s, 50s or even 70s. Hanif was given Stumped on 94 (after scoring 101 in 1st innings) at MCG 1964, when Jarman dislodged the bail with pad first - Umpire gave him on appeal, Jarman sympathized saying, "Hard luck met"; Hanif smiled & walked off - that was it. After WW2, 1st Ashes Test, Brisbane - Bradman wasn't sure if he should continue or not, still he was made Captain; AUS batted & at individual 28, he edged Voce to 2nd slip's chest. England players waited for him to walk - he stood there, Umpire as well - DGB went on to 187; & only a single line from MCC Captain Hammond ended the story then & then - "What a ******* way to start a series". These days, we would have press conference called .................
Allow Umpires to take own decision with the aid of technology - they'll look much better. They are doing it for dubious Catch (with a "Soft" signal) & that's working perfectly. It'll work for every other decision as well - these Umpires are far better than those amateur Oldies umpiring even 25 years back. I wonder what Steve Buckner, Javed Akhter, Khizir Hayat, Ashoka, Pilu Reporter, Tony Crafter, Mark Benson, Tarapore or Banshal will look like these days and I am not going beyond 80s.