Most of my big combats end by the skin of my teeth after having pulled out every spell and ability I have.
And that is absolutely the perfect scenario.
The feeling of achievement is sky rocketing when things work out in the end.
If the victory is achieved by some devious tactics, it only enhances the joy.
I would always prefer a difficult "almost disaster" for a "Ah well. Another six enemies bit the dust. Let's find some more".