NSW Waratahs are ruing their soft defence after being put to the sword in a Super Rugby try-fest in Johannesburg.

Not only caught short of breath at altitude, the Waratahs were caught out eight times by the rampant Lions, whose action-packed 55-36 victory at Ellis Park early on Sunday (AEDT) proved their run to last year's final was no fluke.

Otherwise gallant in the absence of injured Wallabies trio Bernard Foley, Nick Phipps and Will Skelton, the Waratahs paid the price after leaking five tries in the first 35 minutes.

"There are a number of lessons for us," said Waratahs coach Daryl Gibson.

"What I was pleased about is that we scored five tries, relatively easy.

"What we need to do is sort out how we prevent tries and that is more the disappointing thing for us; is how easily we conceded."

The Waratahs suffered a double blow with Phipps (ankle) and Skelton (hamstring) both injured during the captain's run - a day after Foley failed his final concussion test.

Their replacements were handy, especially livewire No.9 Matt Lucas, who forged a decent enough second-choice halves combination with Bryce Hegarty.

But ill-discipline also let the Waratahs down in the helter-skelter, point-a-minute encounter.

The visitors played with 14 men for half the first half after winger Reece Robinson (lifting tackle) and prop Sekope Kepu (professional foul) were both yellow carded.

The Lions' deadly driving maul also troubled the Tahs, with the home side's first two tries coming from the attacking lineout ploy.

Tries from Rob Horne, Michael Hooper and a lovely chip-and-regather effort from Hegarty just before the break had the Waratahs still in the match, trailing 33-24 at halftime.

Hooper, though, lamented his side's defensive lapses as the Lions crossed for three more five-pointers in the second half - to NSW's two from David McDuling and Israel Folau's after-the-siren strike.

"It is a tough place to play. We don't want to make excuses for ourselves. We did come over here to win and we didn't do that today," the skipper said.

"We like coming over to South Africa but the Lions were too good.

"We put in a good hit-out early. Some guys were on debut and some were late call-ups, so I'm proud of the guys there."

The Lions dedicated the victory to centre Rohan Janse van Rensburg's mother, who died during the week.

Her son marked the occasion with a try-scoring double.

"We felt her presence here today and the whole team went out there and played for her," said halfback and man of the match Ross Cronje.

"I just want to wish him and her family all the best."

The Waratahs, after a one-from-two start to their 2017 campaign, now travel to Durban to take on the Sharks next weekend.