Try Rogue, make sure you focus your abilities, upgrade house ASAP and get second ally, Use henchmen as often as needed (i used them a lot...), also get Small Gun skill upto 7 so you can use Laser Gun.
If your still stuck try using the mods (found at start of new game) to make crosshair smaller, or enemies move slower, etc...
Hope this helps... If your REALLY stuck try Casual mode...it'll help you learn a strategy...
The best class is noble. It's unlocked by getting a sheriff to level 10.
I'm on almost day 30 with a level 33 noble. I have two modded MGs, three helpers, and each MG shot does enough damage to kill a sheep or a rat in one hit.
Each time I want to play I find my score/ save games have been removed. I think it's some setting in FF, but I don't know how to fix it. Please advice!