Gear, HP and Stigma aren't the problem here. It's only the positioning.
SW is very hard on movement, that's why ppl use the crack-method (much less moving and so much more save).
You as templar stand on the right back pillar, tank it there and as long as you aren't experienced enough to know when or when not... DON'T move.
To find the correct positioning... just watch Ponci
You need a clear line of sight to your healers in the crack and same time standing on the pillar so not getting hit by the tornados. That seems to be not much, but sometimes it's just an inch of moving and you're dead.
When SW moves to bit someone else... just don't follow him, he's coming back (as long as you done good on your agro job).