Last hit is very good and useful skill! It lands rare, but its still something... compared to that NEVER any warrior had any lethal skill in any chronicle... so you can't or you shouldn't expect that this skill will be simmilar to dagger's ones! Its impossible guys, accept it! Sometimes this skill lands 3x in a row, others it lands 0x out of ten. Plus that you learn it again in upper levels and I expect with more learning to be with more landrate, since it has no power, neither 20%hp break is changed to 30% or so... so in path of logic it should be improved its land rate!
Would be nice if it was faster reuse and like ~40-50% hp. at 20% hp it really only saves you 1-2 seconds on killing the mob anyways. Unless your party is killing god awful slow :/