By level 10 MOST games are already decided. And sure reg and tb get better after 10 but not so much so that they can really stop da or erebus.
The point is that tb reg and qot are soo far down the totem poll there is no reason to even use them now. Erebus oak ub Tier 1. Rook sedna DA Tier 2. tb reg qot tier 3.
Sure a 4v4 game benefits more from a tb or reg, but in a 4v4 game the chances of there being a erebus and a da are super high.
Most games are decided before they begin (eg queen, tb, oak is gernally going to beet da, sedna and a noob with erebus) UB and Oak are the only realy good late game demis they will squash TB and reg any day once towers are gone.
Before the addition of the new demigods it was "Erebus oak ub Tier 1. Rook sedna [DA was removed] Tier 2. tb reg qot tier 3." Only UB extreae dps (from low levels) that does not need mana along with some nice ablity support, is anything close to being good enough to beet priest regen with powerful and versitile abilities.
IF the teir list was broken down it would be:
Erebus ub Tier 1a Oak Tier 1b [though level 3 shield could put it up to the same teir]
Rook sedna [occulas could be here] Tier 2. Ice based tb DA Teir 2.5
From hear you should not be playing these demis unless in the most casual of PUGs and non compdeditive premades.
QOT Teir 3
Fire TB, Reg (Just dont go here) Teir 4 [was not changed when DA was included]
Fire TB and reg are still far worse to play vs Teir 1 demis and sedna than DA, it takes about 30 secs for an oak with DJ to be kited of the creeps by reg and this number gets bigger fast and lets no even factor in that minion dps can force reg back to a tower. No debuffs, interupts or stuns makes your demi weak when your dps not any better than UBs even if you are ranged.