Hack
Not hard to practice. In fact one of the easiest skills to practice (crazy improvement rate unless it was a bug and is not changed). The real problem with skill is 4(!) rounds of lag on success. Many classes can pwn orc in 4 rounds (UNSPEAKABLE holy light and couple of wraiths + Defiance as a good example).
People are not using it more because orcish fights don't last for 40 rounds. Orcs just can't tank for shit to fight like that.
Swat
It has its drawbacks. Nice skill, but overpowered? Pshhh
Same for Brute force.