Ajani's Pridemate would be a sweet card with the WG build... definitely had someone go soul mender T1 into pridemate T2 and clean my clock at the prerelease.
I think the issue people have with lifegain and just completely disregarding it is that it doesn't provide inevitability. But in this deck, with bombs like the soul, the queen, and the wurm, not to mention the synergies between the roaring primadox and some of the etb creatures, I don't think prolonging the game is a bad thing, because this specific deck represents inevitability except against super bomby decks because the top end of your curve is such quality.
Congregate is also a card people do not play around, so it can be effective in games where people think they're going to break parity by creating a massive all-in attack.
Fog, sometimes, win games.
Anyway, definitely a tough sealed pool, and I definitely wouldn't have built this WG deck, I only did it to try something out.