I don't get why people are comparing SAM to MNK. It's blatantly obvious to me that SAM is basically a physical BLM. They have almost no party support and can dish out burst damage.
It requires management of combos and gauge to spend to do anything like BLM manages its stances, Enochian and Ley Lines. It looks like you can't just stand there and spam 1 or 2 WS and do WTFPWNS damage, you need to build it up with the right combos and Iaijutsu first, just like setting up Fire IV and Flare/Foul on BLM.

Both SAM and RDM seems very technical and gimmicky with all the stuff and preparations during their rotations, I wouldn't be worried about seeing SAM everywhere. It'll settle down after a while like it always happens.

(Also the +150% damage for that SAM ability thing appears to be a typo on the English tooltip, other sources like the JP interviews and the likes report a +50%.)