I believe all these 6 countries currently have worst test batting line up in their history.
Australia - Suffering from ban of two best batsmen (who were ranked in top
in ICC test rankings) and another potential great test batsman in
Cameron Bancroft. Team is very demoralised and basically just
waiting for the return of banned trio. Sandpaper gate has hit
them hard.
Pakistan - Struggling a lot financially and due to lack of international cricket
at home. UAE has done heavy damage on domestic record.
Emotional countrymen who love to fantasize on past glory and
put unnecessary pressure on national players. Also being sworn
enemies of the people who run cricket does not help. Their
stubborn nature and mentality to bend their back backwards to
hurt pakistan doesn't help either. Although people from both sides
would love to see a bit more bilateral cricket between us. It would
help their ranking and help our monetary issues

.
Sri Lanka - Still struggling to recover from the retirement of legendary trio
of Dilshan, Mahela and Sanga. Although many would argue
Sanga should have stayed a bit longer as he was in his prime
during retirement. Legends of the past are now a distant
memory as current crop of players do their best to get some
postive results for the team. Succeeding occasionally but still
disappointing on many occasions.
South Africa - Era of Graeme Smith was one of the best batting lineups for
Saffas who now struggle with the loss of worlds best- AB de
Velliers who has chosen the T20 life while having few key
players such as Hashim Amla, de Kock and Faf out of form.
The race quota has only increased uncertainties and added
to batting woes as race is given more importance than merit.
West Indies - The worst effected team from T20 revolution. Losing al key
players due to T20 league priorties took its toll. The people
also don't show the same passion for test cricket as they did
in the past. The carribean T20 league is more glitzy and
attractive. Unfortunately, we won't be seeing rush of local
supporters running into the ground, scaring the crap out of
players, after west indies wins test match against the likes of
Australia. Dominance of batsment like Viv Richards and Brian
Lara in test cricket for windies, unlikely to be seen again
although likes of Shai show some 'Hope'.
Zimbawe - Worst effected team from domestic politics. Mugabe killed
Zimbawe cricket. 1999-2003 probably golden era for the team
and now a distant memory. Only recently Zimbawe test team
survived cancellation of full membership from test cricket. Not
qualifying for next world cup took its toll. Although new ICC
funds and return of key players shower some hope.