As a couple other people said, the most fitting Deck for this card to be in involves using Munna's Ability to put an active Musharna to Sleep while it uses Dream Waltz for 90 damage! That is, after all, a magic number to 2HKO a Pokemon-EX without Eviolite, and a OHKO if its weak to Psychic such as Cresselia EX or Mewtwo EX.
Its physical stats, however, aren't quite as resilient. 60 HP and a Psychic weakness is big Mewtwo EX bait, so make sure you have 2 or 3 Munna on the field by your first turn. 2 Retreat cost means you can't search it out with Heavy Ball, but you can still search it out with Level Ball anyway.
A Musharna Deck as a whole has potential to deal decent damage and disrupt your opponent along the way, but its very reliant on coin-flips, which is a peg down on its consistency.
I'd give it a 5/10 for Playability.