First SE was pretty clear what this staff did there are no hidden effect or anything so honestly i don't think these staffs need a boost.

As for is it useful for the jobs that can use it .... yes

Outside of abyssea

SCH With this staff and use of stragems 1/2mp with af3+2 and sublimation you pretty much will never run out of mp and for Voidwatch atm this is awsome for going through ya spells for Staggers.

BLM... I dunno

SMN
People that acully play SMN do play it solo and by meleeing this staff basically makes that impossible to guage

Inside Abyssea

Sea Daughter + this staff = 20mp+ a tick (better than 3 atmas) for SMN thats amazing for SCH and BLM not so much

Either way the fact it has some unique uses and SE were really clear with what it did means you shouldn't be complaing.

As for ya Mythic stuff.

BLM
Magian gives +25% DMG
BLM Staff gives +50 Mab

Outside abyssea BLM has around 90 MAB in best case

190 MAB + 50 MAB = about a 26% increase in DMG so even if it's 1% the BLM staff is better than all the Trail staffs ooooooooooooooo and u don't need to change staff between nukes so eventully u'll get enough TP to use the Magic attack aftermath o and u get a mdef down effect on the mob which will boost your DMG by another 10% so now your looking at 40% vs 26% outside of abyssea when BLM gets enough tp ofc.

Mythic BLM Staff is the best BLM staff outside of abyssea.

As for the SCH one it's so sititational it sucks but in any case enmity is an issue this staff allows SCH to be the best nuker.