There is also a script command to check for if you are on the GCD or not and will wait till you are not to cancel bear form. I dont remember what it was (have to go look that up).
I have effectively used Brezs on healers in 5mans on many occasions. Its sorta cool cuz the group is like, OMGOSH THAT WAS COOL. I have yet to try this in a 10 man other than say Nightbane inbetween phases and what not. Its all about knowing the situation and knowing your class and remembering that just cuz your tanking something, you can still use your Brez or Innervate even if the situation presents itself.
I cast the spells that make the people fall over.