Attention AST: Lightspeed is one of your better spells, not a bad spell.

[Risvertasashi]

oh hurray, we can use Stoneskin x 7 while running. *rolls eyes so hard they spin*

I take it you're not much of a raider then? There have been times in FCoB... hey even Titan EX back in the day... where I see a DPS eat something optional just before a raidwide hit, and I can't heal nor shield them because I also have to move.

SCH's lustrate shines there. And now, Lightspeed can help with those kind of things too.

That said, I won't argue it isn't situational. It is. Still, making several different spells instacasts is very powerful. Look at it less as a healing buff, and more as a mobility buff. It makes you the bard of healers.

Edit: You're still focusing overmuch on stoneskin and everything but the mobility.

Again, focus on the mobility. Once more, consider Bards. Bards have the big advantage of being able to move while DPS (but as a result, they're a bit behind the other DPS). WM, once fixed, will allow them to exchange that mobility for better damage.
Lightspeed is basically the opposite of WM. It makes you the bard of healers... you can run and gun(heal), but just like bards, at the cost of throughput. Don't use it as a SHTF buff. Do use it to keep up healing through high movement phases. Or shielding, where appropriate, but not focusing on that nor exclusively.