Personally I'd be for slight reskinning of summoner along the lines of what happens to WHM. (eg. Stone later becoming "Glare").

The DoTs could be turned into identical mechanical abilities, just skinned as some sort of micro-summon.

I'd only suggest this if they were ever intending to create a new virus-based mage, or if the bio/virus series of magic had a better fit elsewhere.

Alternatively, I do wish it was rather a sort of choice progression for the big summons.. maybe Bahamut for raw firepower, Phoenix for AoE burn? Maybe a third later on for general DoT/buffs?
Basically allowing one to build up the big summon bar, then summon whichever is best for the situation, or a rotation like Bard's songs so all used, but in an order up to the caster.