"Take 35% less damage." My Rogue has Damage Reduction of about 50%. So if this meant her Damage Reduction went up to 85%, it would be worth considering even at the cost of 1/2 your max health. But the wording suggests to me that that's not how it works. Let's do an example with numbers. Suppose an enemy is about to hit Rogue for 10000 points of damage. "35% less" means that becomes 6500 points of damage. Now apply 50% Damage Reduction: 3250 points of damage hits Rogue. 10000 -> 3250 is reduction of 67.5%, not 85%. The Attack Speed increase tops out at 8.85% for 50 ranks. 67.5% Damage Reduction seems like a lot, but if you're only at 16K max health? I dunno ... has anybody actually tried this?
Oh, and while we're on the subject of useless powers: Simian Strength? What? What were they smoking at Gaz to come up with that? It might be usable without the "must be at less than 60% health part, " but as it is ...