Benediction does pull a lot of hate, since it's such a huge burst heal. In all cases, it's worth using if it means the tank will die otherwise. Also, if the tank can't pull hate back him him/herself, then it's less of a problem of Benediction's enmity generation as it is one of a tank being able to maintain aggro.

I regularly run with tanks that can keep hate even while I'm spamming Holy and following up with a clutch Benediction to save them.