Lord knows my 2 handed Man-At-Arms kills everything but a boss in 2 hits.
Mine too. That doesn't solve the problem though.
All of my fights except for MAJOR boss fights take under 2 minutes to resolve. It takes less than a second for my mage to cast any of her spells except very specific ones. The enemy round is usually over in under 1 minute.
If it is taking your characters longer than my characters to perform actions, maybe there is something wrong with your graphics card or the drivers? I know some games slow down for older graphics cards even if they supposedly meet the 'minimum specs'.
I had that problem with Might & Magic X. Every step took nearly 6 seconds until I bought a new graphics card, and then every step was a fraction of a second.