Nope, its not.
At the higher hero levels, matches don’t last that long (typically 10 turns or less) which largely nullifies the long term value of the 3rd trait.
At the lower hero levels, chances are this won’t be traited or you won’t have King Silenus traited (or owned).
Its the same reason that Death’s 3rd trait is largely useless as well. (Yao Guai/Nimue/High King Irongut’s 3rd trait are slightly less useless as it can trigger multiple times per player turn)
At 24 mana, the stuns just takes too long to be reliable (and can’t target stealthy troops anyways.) 3x stun will hit most targets, but situations like normal, stealthy, stealthy, normal (bandits) will interfere with proper casts.
3 stuns are nice, but Emperor Khorvash at 14 mana is just easier to use under most cases which stuns the front 2 on cast and can eventually randomly stun anything/everything.
This can be taken down to 12 mana to cast for the first time if you’re willing to burden yourself with a very underwelming King Silenus on your team.
At 24 mana, you could probably find a way to kill your stealthy/submerged enemies faster than doing 30/60/30ish dmg to 3 targets and stunning them.
As for the Monkey Disciples, they’re just unreliable troops. It can stall out skull bashing teams like Cedric + Bombots can, but Tian Yi doesn’t have the Stealthy protection to make that super viable for defense. On offense, it’ll work in your favor to stall out matches like that, but why let it get to that position in the first place if you could just use a more reliable damage dealer in the first place?
If they added Stun all Stealthy enemies to its spell, then Tian Yi could have a unique purpose even if situational.