Generally, the game gets easier as it goes on. There's a bit of a difficulty spike at the ToEF, and again at the Mana Temple, but generally surviving to Dwarftown is the most dangerous section of the game.
You simply have more resources available to you the farther you go, more HP/PV to avoid sudden deaths, higher speed, etc. There aren't that many high level monster abilities that are particularly threatening, and it's fairly easy to bypass anything you don't want to deal with via teleport or other means. The good news is that the endgame is quite short--from the moment you finish the ToEF to the moment you finish the game is only a few hours' play time.
Hoping to win with every class, doomed. Archer, Barbarian, Bard, Beastfighter, Druid, Elementalist, Farmer, Fighter, Monk, and ULE Priest down.