Set a fourth-innings record 539 for victory, Australia were all out for 361.
Only Usman Khawaja (97) and Peter Nevill (60no) showed any true grit in the chase after the middle order folded meekly and they missed a huge opportunity to post a big first-innings score after David Warner and Shaun Marsh had set a solid platform.
"As individuals, the Australian players are under huge pressure. They have lost four test matches in a row," said Wessels, who played 24 tests for Australia during South Africa's isolation from international cricket.
"This means that captain Steve Smith, in particular, is under the pump. His captaincy in this test match was unimpressive.
"He isn't in the best form with the bat either, which compounds the problem for him personally and for the team as a whole."
Set to come under some of the most scrutiny in Hobart will be allrounder Mitch Marsh, who continues to struggle with the bat.
Marsh, who took two wickets for the match on his home ground in the series opener, averages just 23.18 in his 19 tests batting in the middle order.
"They have a long tail with allrounder Mitchell Marsh batting at six," said Wessels.
"If the Australian selectors had any sense they would pick six specialist batsmen and opt for four front-line bowlers.
"This will give their team a better balance under Australian conditions."
Australian selector Mark Waugh has challenged the top order to sharpen up mentally after he was left dismayed by their latest batting capitulation.
Waugh was still scratching his head 24 hours after watching Steve Smith's side slump to a 177-run loss in Perth after having South Africa on the ropes on day two.
"The facts are it was disappointing. I mean, we shouldn't lose from that position, really," Waugh said on Fox Sports' Inside Cricket programme. "We've seen it happen probably three or four times in the last five test matches where we've dominated day one, we've been ahead in the game and then I don't know whether it's a subconscious thing where we relax a bit.
"But South Africa played great. Full credit to them. But if our boys look at their performances, they'll know they can do a lot better than that."
Even South African great Shaun Pollock was "still trying to work it out" after the visitors inflicted the first defeat on Australia in the opening test of the summer in 28 years. And the Proteas did it without pace spearhead Dale Steyn, who broke down just one wicket into Australia's second innings.
"It was a combination of some good bowling and some poor execution with the bat; poor decision making," Waugh said. "I think it's a bit of a mental thing now, possibly. We've had it happen to us probably three or four times in recent times - in Sri Lanka. We go back to England, that was a while ago.
"You've got to have your plans in if it's that sort of bowling. At the moment it looks like we're batting and hoping a little bit."
