To me this reads more like a bug fix or oversight correction than a true nerf. It's a channelled ability that should probably act like a channelled ability and it may have been technical limitations or simply greater priorities that left it in the current state. PvP may have bumped it up the attention ladder a bit but the change still feels logical and sound to me.

I think that concerns the change leaves the ability unduly weaker in PvE are also valid but there are probably ways to correct the problem that don't require putting it back in the odd channelled-but-not-really state.