It's not so hard to be better than a pure fighter, specially since the fighter kits' perks start losing edge once your casters come up with better counters to disabling spells (I'm looking at you, berserker!).
The only real contender here is the fighter/cleric multi, and honestly the PoL can buff himself to be WAY more effective than the F/C. Sure, it's on a timer, but for its duration (long enough in mid levels to handle most tough fights, and goes on for minutes in higher levels) you're a God. 5 APR (boon+haste) , a better thac0 than F/C (Holy Power+faster leveling), better saves sooner (assuming dwarf both cases), more spells (buffs, debuffs, cc, dmg), better turn undead, better everything.
Convince me otherwise.
The one thing going for F/C is greater whirlwind, and it's a one-trick pony. Also, subjectively better stronghold (castle > temple). Totally unrelated but: I think Priest of Tempus should get the castle instead (pls, Beamdog).