Where to start, while I agree with some of the things stated about Healing focus right now not being very useful for raid encounters and could be used elsewhere I have to take into account the fact that I constantly do heroics on top of raiding and thus it wouldn't make sense for me to drop healing focus or respec every day simply for the additional 2 points I would gain.
True overhealing doesn't really matter if you do have the mana, back when the pally glyph was just changed to be OP we did a naxx 25 and our pally overhealed almost 40 million which would by most cases be sad when you consider his healing for the fights was only 17 million. But he had the mana so it didn't really matter all that much. But as blizzard has stated mana is soon going to become more important and do you want to learn how to play your class healing inefficiently simply so you can top your charts and then further fall on your face when you don't have the necessary mana? Overhealing is good but not necessary, even to predict damage, there are plenty of addon's that show agro to a person which makes predicting damage that much easy, then of course there is always the ever better "Just know the fight" tactic.
A balance of haste and crit is vital I think, having a 2.1 second greater heal is nice trust me, pop heroism and I've dropped to a 1.16 second cast on Greater healing, making it during heroism more viable then flash, or my less then a second flash. The trinket is nice, but as soon as I find something viable to replace it, you can believe it will be gone.