In many heroic boss fights any damage the healers can do is significant. Calling the damage negligible is bad especially when you don't know what it will hit for at level 90. I do think the cast time is too long, making it an instant should not make it too powerful. It also helps on the short duration. Instant cast makes the downtime only 4 sec, something I feel is just the right amount. I'm not sure another AoE, conal or otherwise, is something Elemental and Enhancement need nor is it something I think Restoration needs. I do feel like the only way to make Elemental Blast attractive for Restoration without nerfing the other two talents or making it heal is to make it instant cast and maybe increase the buff to 7-8%.
Do we know if the stat it boosts is random or does it pick whichever you have the most of? The latter is preferable but if the stat trend now for Restoration is the same in MoP it wont matter which it picks.