The thing is, as a sage healer you don't get nearly enough support from your team mates.
I play a healer-sage in 40 arena and the vast amount of time my teamates let me get ganked upon while running after (anything else reallly) bunnies.
As is probably know very well, 40 doesn't exactly have much of what-is-called teamwork. Ideally yes you're right tho, the ability to stealht, root, rb, rez heal make them great healers.
Need to get some xtal damage in too to actually get some points.