It depends on whether 'strongest' is only a matter of dishing out as much damage as possible. An Abjurer sure isn't ahead in that race, but if the raging barbarian gets an extra turn of being alive thanks to arcane ward, is that powerful? I'd say yes. But I'm thinking in tabletop terms here. With double-tripple fireballs and disintegrates per turn being a thing, no amount of teamwork will beat a surprise nuke.
If Larian doesn't impose the 1 spell per turn limit, a hasted Evoker is going to have some insane blasting power. That said, they'll still be behind draconic sorcerers with the same setup casting up to 3 fireballs per turn, and only a bit ahead of other wizards with up to 5 damage per spell.
I think it's worth looking at other things than squeezing out the biggest theoretical damage number too. Imo Diviner's Portent is the most broken ability available to a wizards. It may not be as flashy as melting a whole patrol of githyanki soldiers in one turn, but the ability to just decide the biggest threat on the battlefield autofails their saving throw against Banishment or your Disintegrate 100% connects with no checks is incredible and possibly stronger than an extra 5 points of damage as it stands.
