Lvl your guys to at least 4-5. Maybe change a chemist to a blm, and a Squire to a knight. Let Delita and Arg take care of the Archers on the roof and be sure to give them the items ability. Everyone else should rush for the blm on the ground straight ahead of them.
That's at least what I did.
I want something good to die for To make it beautiful to live. Queens Of The Stoneage
Here, this is just a quick rundown of basic gameplay tips, and I'll give you some tips on dorter shortly.
Play the tutorials, dont *ever* let your characters turn into crystals/chests this means you lose them permanently.
Always try to have your characters doing something (to gain jp), use a balanced team (ie, 2-3 damage dealers, 1-2 healer/support, 1 damage spellcaster ect) , don't split up, focus fire your enemies (a half dead enemy does just as much damage as a full health one, killing things reduces the damage you take, taking damage is a bad thing).
Always have a method to bring your characters back to life, frequently update equipment it helps in the early game as equipment can either provide evade (shields/mantles) or bonus hp/mana, Dragging around a chemist and another character with items is a good idea in the early game.
Its not necessary to stay in jobs till you master them, in the early game it helps greatly to move onto jobs like monk or black mage as they're don't suck like squires do (squires have a great skillset for what they do, but monks are just plain better), having a spellcaster in the early game is a big help because a bolt or ice 2, will kill things dead, FAST.
Switch your guests into knights, and get them a decent set of equipment, but priority goes to the characters you use to fight random battles.
Now... for the dorter section of this. Dorter is the first noob-killer of the game, and you *will* find more battles that are atrociously hard the first time if you approach them wrong.
If you're still in your base classes (squires chemists), you're doing it wrong, you're fighting knights with their armor (these ones possibly only have robes I don't remember), Archers, and black mages, going into this with base classes is stupid.
Two of these classes have an obvious advantage over you, with good to high damage ranged attacks (magic and arrows), fight fire with fire (or in this case, use lots of bolt magic, it gets a damage bonus when its raining).
Delita and Algus will always try to go after the archer first, keep whoever that archer is targeting healed, let the first knight and black mage run towards you, then lay into them with spells/swords (be mindful not to let your own characters get hit), after that you have another mage or two to mop up and a few unarmed archers, have fun.
Farewell Monster Hunter. The black wind howls again... As you are, I once was, As I am, You will be.
SyfaOmnis is right, don't stick to the base job. Have at least 2-3 long range characters here (since there's a "lot" of terrain advantages here, get at least an archer or two). Chemist class will also be of help here, if you have a white mage with healing skills, the better.
"Civilizations that undermine the value of life will fall..." -Atelier Iris-