I think you made a mistake starting the game as Hard as your first playthrough. Hard is
hard. Do explore everywhere you can without fighting anyone or fighting weaker enemies; be sure to buy a boat also.
Human troops aren't actually that great, so it's a good thing you're running out. If they were good, then there wouldn't be much point in other units, would there?
Toss out the monks (they're pretty terrible except for against undead), and instead, for example, get some bears, or blue (royal) snakes from the swamp if your game has them.
Make liberal use of the Slow spell and focus attacks on one stack at a time. Remember you can Wait to let the enemy make their move first. Most of the stacks you'll fight in the game will be even, hard or very hard.