70% chance to cleanse
30% chance to get the buff
30% chance that the buff will do something
6,3% chance per cleanse to get something.
??? ???
No profit!
Don't manipulate maths itself, it is an exact science, which u just need to input CORRECT data and it gives the result
The tooltip says: Your Cleanse spell has a 30% chance to increase the target's resistance to Disease, Magic and Poison by 30% for 10 sec.
So basically ur cleanse (
any cleanse, not just sucessful ones) has a 30% chance to apply this buff on any target. U don't need to even be poisoned or slowed to have this buff. The buff target, recieves a 30% resist chance increase to poison/magic/disease, which lasts for 10 secs
As ur a one target healer, having the possibilitty of even preventing damage and effects on multiple targets and yourself for some time, i would say it is pretty valuable. It's also about taste, but personally i like it. U don't even have to do maths, just try it yourself and u'll see if it's useful or not. On lower arena ladders it is arguable, but in 5v5, bg's, and raids, it's a much much better choice then the 3% crit from holy power, for example.
As for OP question, in pala/arms team this buff can be pretty useful, as it prevents much of CC on ur warrior, which is a key for letting him reach is target and sucessfully kill him, it's as though an additional Hand of freedom on them, with a bonus resistance to it's effects. It's pretty usefull with pala/hunter team too.