You start to see the case for blur40,000 GP item? Schroedingers Wizard is alive and well.
Trip does largely the same thing. Melee touch attack (+9 vs Touch AC 21), then a Strength check (with +4 for size) at +10 v the Dexterity of +5 for the Bladesinger.
Prone grants -4 to AC, for a much more manageable AC of 26, meaning the Trolls hit with claws on a 17+
His HD are d4's.
Id likely get them to Overrun (+10 vs the Elfs +0) the Prone Elf at that point though, if that clears the choke point.