Hi @ash elemental,
Flaming sphere is quite an "overpower" spell indeed - but again, allowed by the engine. But to make it more "cheese" or "cheese^2" (if there is such definition), here some ideas on how to use it.
keep your party at distance, or hidden, as you said, then cast the flaming sphere and start attacking vilains with the sphere and then:
That is actually what my screenshot is showing (party is hidden). I think it's cheese not due to the spell itself, but due to how the enemies for some reason consider the sphere an opponent they can melee. Enemies should recognize it as a spell effect and, failing to damage it, they should move away instead. I suspect the sphere is coded as a summon/npc of sorts and hence the weird enemy behaviour.
