Here’s what I’ll tell you (briefly).
1.) Generally, people love warriors for raiding because they do a lot of damage and can tank.
I won’t tell you not to roll warrior, just know there appear to be a lot of warriors per the census done on DD and you will be competing for equipment.
Rolling warrior (if you are competitive) generally means PVPing at some point for gear, because your PVP gear is good in PVE. You don’t have to, but know that a lot of warriors will PVP for the gear to use in PVP and in PVE raid progression.
We’re not currently using PVP gear in PVE if your adhering to the phase structure that’s currently in place, but eventually PVP gear will be used in PVE.
If you do not PVP and get items like the HWL armor/weapon - just remember that Classic WoW raids don’t drop a ton of loot. There is a finite amount of loot…which means Raid Weapon upgrades do not come regularly.
Back in 2019 playing a Mage, I did not replace Mageblade until Naxx when I replaced it with Wraith Blade.
As a warrior, your weapons are a big part of your damage and competition for those weapons will be fierce.
If your knowledgeable about the game you already know this, I’m just reminding you.
2.) I do not recommend that you go Blacksmith.
Simply put, you are coming in a few months in and it’s certainly not too late to start fresh on DD.
That said, you will eventually be joining a raid guild, and any established raid guild on DD has Guild Blacksmiths already.
Unless you want to torture yourself and grind Blacksmithing up yourself…utilize other professions. You’ll almost assuredly end up being a Blacksmith with less or potentially no rare recipes.
Our guild’s blacksmiths got funnelled. They are Blacksmithing as a sacrifice, because they are dedicated to the guild and picked up that profession to make armor or weapons on behalf of the guild to assist with aggregate progression at the expense of themselves. Most of them were provided with raw materials for free (lots of them) to help them more quickly level it up.
3.) If you are looking for a class that people on DD are going to actively want Horde side, I would say roll Priest.
They give excellent group buffs. They are a favored healer in general because of their healing ability and shield. It will be easier to find groups (unless your a warrior who tanks) - and even then it’s close.
There is not a glut of Priests at the moment Horde side. I cannot speak for Alliance.