UB - I've tried Wrath Builds before using Heavan's Wrath to level quickly. You can use Wrath to break Grasp which is somewhat useful but only if you're playing demigods without any stuns to just stun you back (Sedna, Oak, Queen, Reg) and therefore you just burned your mana for it...
Only an effective very-late game (then it's crazy...) but you won't get there unless you're playing newbs.
Sedna - Yetis
Oak - Last Stand should give some sort of passive buff, similar to how Poison Blood is.
Queen- Compost + Uproot. Uproot is just terrible. Shamblers would be better if they just fixed the horrendous targeting and pathing they have (issue a comman to them to walk to the middle of a creep wave so you can mulch them... yeah. It won't work 90% of the time). Most Level 15 skills.
Reg - all level 15 skills, pretty much. Fine other than that though.
Rook - Transfer... some good players get it butI've never considered it particularily good just because you hurt yourself more than you heal if you do it to the wrong place. God Strength seems useless with Rook's low attack speed and then he gets Cleave/Throw-back if you get his weapon damage high enough anyway.
Erebus - All good, Poison Blood is sorta weak, I s'pose but most people get it for the very high HP regen anyway. And the fact it's a fear-tactic.
TB - all good
--
that said, in general a lot of the Level 15 skills seem lacking:
UB - Foul Grasp III (and II, really)
Sed- the <30% hp== +50 hps one. End game if you're at 30% hp, you are dead within seconds, unless you have a sigil on (raised to an Aura possibly, maybe make all abilities cost 0 mana or very little mana). Pounce's level 15 isn't useful either, since ... no one uses minions on Sed. If Yeti's were made viable, it might become better. Yeti's final skill... but it's yetis so.
Rook - Strut transfer, 150% mana only after using a skill isn't much... TB has +200% regen AND +15% pool as his level 15
QoT - Tribute... Violent Siege