He didn't say you lose effective healing with rapid rejuv, but that it was "not particularly useful" because it doesn't increase the healing done by a single rejuv. The point is that, either way, you expect most of your rejuv to be effective, compared to a fight with less well-distributed damage, where the faster ticks means that you're more likely to get ticks that are effective.

I can see how your healing strategy could work well, but for twins at least, imprecise blanketing is more than sufficient; I've never found that precise healing assignments such as you describe help me much in raid healing (standard caveat of "every raid should do what works best").

The ramp-up time is an interesting argument for some things perhaps, but at least on twins, it's quite easy to have your rejuvs rolling before the pull making that particular line moot.

It really depends where you cast it primarily which is what gives strength or weakness to the glyph. I tend to throw it into melee personally since they benefit from Revitalize and I have a good chance of hitting at least 5 targets. If I see a ranged group that has that many people I will use it there as well. How good that glyph is depends on how good the person casting WG is at putting in a place that will make the most use of it consistently. That's not to say it's wasted on a smaller group (it can still be useful). It just really requires that you look at your screen when you cast it if you're looking to always hit the maximum amount of targets (as opposed to tunneling on grid).