Generally yes...though Word of Glory on yourself is fine. Also realize while casting you can't dodge/block/parry afaik. As far as threat goes, it's split evenly between all targets, so if you have 5 mobs, you're only getting 1/5th the healing threat per mob.
All that being said, if adds are spawning from 4 different corners of a room, a heal isn't a bad call, since it's hard to actually attack all of them.
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