Overall MP (sans Manafont) still limits you to F4x6 + F1 + Despair; the extra time on AF simply allows flexibility (which is extremely nice) … and Manafont can always be used when you get a Firestarter proc (i.e. F4x3 > F1 > F4x3 > F3 (proc) > Manafont (weave) > F4x2 > Despair).
Leading with F4x4 does have some merit though, in that Despair has a longer cast than F1, but I often finding myself limited by the Thundercloud timer (proc with Sharcast during UI phase) as I'm assuming 100% Thunder uptime is a good thing.
From testing, using Freeze over F3+F4 is practically break even and IMO any theoretical gain isn't worth the timing issues... i.e. the Freeze rotation (sans Lay Lines; which breaks it) is almost exactly 30s, so if don't have a Xenoglossy (which you won't the first time around) or a Thundercloud proc, there is a risk of having to wait on an MP tick after Freeze and / or the Sharpcast timer. The standard F3+F4 rotation, being longer than 30s, does not have these issues and even leaves you with the occasional spare Xenoglossy (which is useful for movement).
I'll have to try it, I've being doing:
Triple Cast > B3 > Enochian (weave) > B4 > Sharpcast (weave) > Thunder 3 > Laylines (weave) > F3 > F4x3 > F1 > Thunder 3 (proc) > F4x3 > (if Firestarter: F3 > Manafont (weave) > F4x2 >) Despair > B3 > Xenoglossy > Sharpcast (weave) > B4 / Thunder III (order depends on Thunder proc) > F3 ... repeat.
Which is a slower start, but I find the timing quite nice and it puts me into a good rhythm (until I get targeted by random AoEs and it all goes to hell).
Manaward is better than most self heals.
Edit: On topic, BLM is definitely the best it has ever been, both in terms of gameplay and (potentially) having a place at the meta table. There are still a few small improvements that can be made but considering the state of certain other jobs I'd be happy enough if BLM just stayed where it was for the rest of ShB.