Technically.... One could argue that SMN is the best magical damage dealer.
Especially now with all the pet MAB gear it has.... 150MAB is practically average for a SMN these days.
Better than BLM or SCH because we don't have to worry about enmity gain... Cause once the mob kills the Avatar... just poop another!
And considering the natural refresh rate... and the HUGE regain of MP from Elemental Siphon... SMN at 99 should never have any MP problems.

And I don't think formless is OP.

I think that Delve is a tad too demanding of spots... (X of these, Y of that job etc)
And considering I can't really recall the last time MNKs were having their heyday at the top...
I am all for letting them take the spotlight in Delve...

For now anyways... There really should be more wiggle room and varied playstyle than what Delve currently supports.

This is really more "I think Delve is dumb" rather than a real "formless needs rethinking"...
The problem is the event... not the job.
At least in this case.