Wait how are you finding fighter easier than assassin?! If anything the assassin is just a fighter with more options available, less defense sure but he makes up for that with the short bow and being able to just 5fold arrow into weakspots. Seriously, downing a liquid vim and spamming 5 fold arrow at anythings weak spot will drop it in a matter of seconds.
The fighter has what? Dragon's Maw, which amazing damage but really risky as well as the positioning of the attack being a bit important.
The fighter is awesome definitely, but how is it easier?