I'd rather have no instant as BLM than Scathe, since its dmg is absolutely not calculateable. If you luck, you get the double damage proc and if not, well gz to an Instant which does less dmg than a fire I without Astral Fire Stacks, which is enormous low (compared to the rest)
Aetherial Manipulation lost its usefulness after Ifrit for Eruption, most battlefields for bosses are just not big enough to use it effective.
The only DoT from the BLM is bound to a fairly long cast-time (depends if I, II or III) and with a 5% chance on tick to get a free-proc, well we dont calculate RNG to the mobility shooting while running or do we? And dont tell me that WE got swiftcast, evrey 60 seconds one instant skill is not enough to throw "efficient" damage.

But to get something useful out of here, they should increase the TP bar like the normal MP bar with levels and/or equipment and just fix the Sprint to not cost TP and just give a regular runspeed increase for a few seconds, doesnt have to be 20