The only event my guild really uses DA ramp for is jelvan, and that is just to make it a bit easier. I suppose we just don't utilize it enough or something, but it hasn't ever been an issue. We have used it on council of the nine, various other anguish bosses, and a few Tacvi encounters, but like I said, ramp tanking was never a big issue for us. Given that i'd have never made it a "requirement" for my guild. There, however, are plane of time raiding guilds on my server that DO require it. It really depends mostly on if your guild utilizes it or not I suppose.
NOTE: Don't flame me for not "utilizing it" or whatever
. I was never a raid leader and only lead minor events like don dragons, etc. So it wasn't my call.
ANOTHER TOTALLY RELEVANT NOTE: If you're going to use DA ramp, 90% of it is good communication with whomever is healing you. It wasn't an issue for me since I
always boxed my own cleric, but you will die pretty fast if you assume they know when to heal you, when you are DAed, etc.