Eh, that fight is sloggy though. The giant has basically one trick, move to melee range and thump with club. Meanwhile AC25 (reflex is 23) means you've got PCs hitting on around a 17, maybe 15 at the very best. It will be a long slow process. If the PCs play fairly optimum tactics you're looking at around 4 rounds of full up everyone aiming at the giant to kill. I agree, you can make a successful encounter out of that, but it is far from ideal. It has a club doing 3d10+11 damage (average 27.5 per hit and with a +11 it will be getting in some hits).
Typical 11th level Brute AC is 23. It worked fine with 4th level PCs IMC, they were hitting it on a 12 or 13 I think, and I seem to recall some buffs/nerfs being deployed. The goblin allies kept things lively too. The Controller PCs put plenty of effort into locking down the giant & nerfing it so it couldn't splat the melee PCs.