You have a couple of options besides that, though they will take longer.
The most straightforward, if you're using a Warrior or Scout as your hero, is simply leveling him up big-time. A level 30 warrior with a few bits of decent gear from the various locations you can explore is a force to be reckoned with even on his own. A scout requires some support even at high levels, but give him that and he, too, can wipe the floor with quite powerful guards.
The second option is to look around for creature lairs where you can recruit higher-rank units. For example, a Sorcery Store lets you recruit Gargoyles, a very resilient 2nd rank unit that works well as a buffer for a scout to get off more shots. Other potential units for hire are Dryads (2nd rank), Harpies (2nd rank) and Trolls (3rd rank), either of which are a step up from the units you can build yourself. They may not be easy to get, though, some requiring a high diplomacy skill (and thus a Scout hero), and I can't remember offhand whether their lairs are actually present in the tutorial.
Finally, you can simply level up your units and work to get them some medals. A 1st rank unit at level ten with three medals will be able to stand up to most of the 3rd rank units in the game, and steamroll 2nd rank units. Can be tricky though, as you obviously can't afford to lose any of your units while doing this. Bring healing spells!
Post edited January 11, 2013 by Zhade