It might have sucked in 3.5, but in Pathfinder summoning is really good. Your Vrock for example was moved down from SM8 to SM7, so now it's showing up on a CR 13 battlefield with the same to-hit it had before. Since CR 13 monsters have an average AC of 26, with Augment Summoning that means it hits on a 9 with all 5 of its attacks, and that's before things like flanking or its heroism buff come into play.
Even in 3.5, a force multiplier like a bard or the right battlefield control could make summons pretty handy.