... (with the partial exception of MM9) is the bow. Get all your characters the bow skill and arm them with one asap. Then learn to fire a continuous stream of arrows (a) while retreating (the "shoot'n scoot") for use in dungeons, and (b) while moving sideways for use outdoors. The latter won't do much for your accuracy, but it will destroy your opponents accuracy until they get really close in.Melée fighting is a last resort unless you really do outclass your opponents. The most effective combat spell in the book is the Dark Magic spell "Shrapmetal", when it is cast close up & personal (i.e. contact range) by a caster having 20+ skill levels in Dark Magic. It also helps if they are wearing an item "of Dark Magic". This increases your effective skill by 50%. Then it does horrendous damage, very reliably, unless the opponent is immune.
The two critical stats for fighters are strength and accuracy. The latter determines how often you hit, and the former how much damage you do. In a tough fight, go turn-based so that you can pick your fighting tactics. If in trouble, RUN AWAY; your party will be faster than your opponents. And keep in a situation where you CAN run away - thinking here of clearing The Pit with a Light Path party. Don't get too far away from the door to the Hall of the Pit, i.e. within one turn-based move - and I mean one, not two.
HTH! 
