Many of the enemies in Tactics cast infinite spells, and have more hit-points, lower AC and such than they would have according to pen & paper AD&D. That's what people refer to when they say the enemies in Tactics use 'cheese,' I think.
If you're looking for a mod that improved enemy AI and makes boss-fights a little harder, there are other mods around which employ no such 'cheats.' Look for them on
Gibberlings Three,
Spellhold Studios or
Pocket Plane Group, for example.
That said, I believe Westley Weimer has developed Tactics, and his many other excellent mods, purely out of love for the game. All the fights can be beaten without extreme use of cheese (to be honest, the way he's improved the AI of bosses, there isn't much room left for cheese).
Two things I can think of which might especially help if you have trouble beating a Weimer-improved encounter:
1: Use all the resources at your disposal. The fights are balanced for you to use pretty much every wand, scroll and potion at your disposal.
2: Bring people who can buff up your group, and strip away protections from your enemies.