PvE: Top tier in AoE, probably even the best class in burst aoe. But top tier single target? What are you on about? They're good, but really far away from top tier in ST.
Instanced PvP: They already got a few nerfs, e.g. 85% primary on the template and FoF / SotWL at 70%. I haven't seen any complaints about them there since then. Until now, obviously. So: No idea if that was enough or wasn't.
World PvP: Yes, I've even heard stories that WWs were able to do more damage than the amount an affliction warlock could heal and shield itself.
On a more serious note: Yep, awesome burst. It probably will be a really strong class there.
I'll wait and see. Though, historically, the spec scaled badly with gear (except weapons). If they haven't fixed that, they will shine in quest / dungeon gear, and a nerf will come. This will make the class too weak in raid / mythic+ / high crafted / high PvP gear, as it was in WoD - except in mythic+, their toolkit really shines there.