First off is there a specific quest order that players follow to slowly gain experience. I would imagine doing the hag quest would require a high level good geared party to tackle it.
Quest order is pretty flexible really, just depending on how confident you are at tackling different things (Like, going after the Gnolls might be done a bit later)
The main thing to do is ensure you complete ALL of the Grove quests before initiating the Goblin Camp sequences (Either causing the attack on the Grove or killing Dror Ragzlin). Since doing so will cause any uncompleted quests to be unavailable (Things like saving the kid from the Harpies, confronting Kagha, stealing the Idol, helping Sazza)
Second, I was thinking of trying to make a fighter/cleric because I want to make a melee character that has good AC and damage.
In terms of good AC, it's normally Dex based classes that have the best AC due to the fact that Dex provides AC.
A Dex/Wis Monk will have the best AC in the game and after level 6 as Open Hand they'll also be dishing out crazy damage. Rogues, Dex Rangers, Dex/Con Barbarian and Dex Fighter can also get good AC (Though this will usually kick in during Act 2 when you can purchase Yuan-Ti Mail which is medium armour that doesn't have a cap on its Dex bonus to AC - The exception is Barbarian because they can use robes/clothes and get their Con modifier to AC like Monks do with Wis)
Barbarian also gets the benefit of resistances (Reduced damage by 50%) while Raging. Normally just physical damage (Slashing/Blunt/Piercing) but Bear Wildheart provides resistance to everything but Psychic (Which you won't encounter until the end of Act 2)
Though, if you want a character that is super unkillable... Melee Wizard. 5 levels of Fighter (Eldritch Knight) to get second attack and equipment proficiencies (Get the Shield spell) the rest of your levels as Wizard (Abjuration School) and hoard every single item that provides you with the use of an Abjuration spell (And pick those spells as you level up) to use after each rest (To stack up Arcane Ward). Get some Heavy Armour (Ideally you're looking for Heavy Armour that has a passive effect of reduciing damage taken, the earliest you can find this is in Grymforge) and the Heavy Armour Mastery feat. You'll take very little damage at all and if you throw in a Warding Bond from a Cleric you'll likely take 0 damage from practically everything.
With Melee Wizard you can ignore most spells and thus spell stats (Abjuration spells don't have spell stat scaled effects or any DC's) and simply go full Str and slap things with big 2 handed weapon. Spell slots simply are used to cast Shield or to generate Arcane Ward charges for damage reduction.
