I would highly recommend my Immortal Commando.
This build is beginner friendly. Just follow the devotion path, max out Vindictive Flame, Veterancy, Menhir’s Bulwark and grab mortar/canister/BWC to have a decent damage output. Can also level through fire strike if you like. One thing is guaranteed, you won’t lose your char. Make sure to farm the green shield on your way to Homestead and you will be set to survive the nastiest situations. Just don’t neglect resistances, especially in Elite and Ultimate.
There’s another build I was gonna post here (5x damage, similar toughness, nearly immortal and very very easy to level without any risk of dying or need of rare items), but after discussing it on a different forum, the decision was made not to disclose it. I feel bad about it. This constant fear of nerfs is not healthy for the community and the game in general. But it’s there because devs put too much focus on ‘balancing’ things instead of addressing bugs, some of which have been ignored since GD launch. People are afraid to post really creative builds, because, more often than not, those are deemed as unintended synergies/mechanics and quickly reduced to ashes. It happens so fast, that beginners don’t even have time to try these builds. Why not let players enjoy something special? So what if it’s a new king and it stomps someone’s favorite build?
Anyway, back on topic, warlord is also very good, but be careful about reflect damage. I lost a couple retaliation toons already. While the risk is low in SR or Crucible, it’s very very high in campaign, where even white trash mages can oneshot you with their reflect auras if your reflect resistance is too low while the damage is high.
Another good HC class is Spellbinder (AAR). It’s quite tanky and easy to level/gear.
Good old Death Knight is another great starting class. You can begin farming the Krieg set on Elite at lvl 75 and have a fully ready DK tank by 94. This can be a good starting point to farm endgame gear.
I would avoid any glassy builds on your first couple playthroughs. Get some gear, relics, crafting mats and blueprints, then go nuts experimenting.
Good luck!