well they actually can do that for sure... if the dmg and the mechanics are designed the way that you'll have to compensate way more impact than just tank busters the whole design for one pure healer and only one utility healer is easily set. sure the comm would cry for whatever reason but I don't see a problem with that. the grps have to chose between sch and ast for the 2nd spot if whm would be pre set as raid healer in 4.0.

pure healer isnt in demand yet but who knows how 4.0 turns out? let's see ^^