For anyone with multiples of a class who has been regretting it, now is a good time to delete and reroll. Its not that painful at all.
I've been running with two warlocks (and a titan) since launch and regretting it since TDB since it hasn't really done much especially with DIM addon. Finally this week I bit the bullet, deleted my second warlock, and rolled a hunter. I figure with a bunch of time sitting down watching E3 streams it'd be a good time to play Destiny in binge mode with the sound off. I was going in with very little gear, I had a single exotic helm and an exotic chest from engrams but I do have two other 34s.
I hit level 11 in the first day after 4 hours or so of quests, and 20 on the second day with another 5 hours. Today (third day) I am 32 after using an armor core for gloves, running VoG (normal) in a LFG pug and getting chest/pants. I'll run POE 34/35 on my mains and burn some judgement chances this weekend, my character is 34 the second I finish leveling the VOG gear.
So yeah, less than 20 hours total and pretty painless, obviously if I was starting from scratch I'd be missing weapons and cores and etherics so it'd take 2-3 weeks to grind out the marks.
Only thing I'd say is swap to the right class before you get to far in and don't bother doing any strikes from 1-18, they are a huge waste of time. I wasted an hour in a matchmaker Devils lair. At 18 you can start earning marks so thats a good time to start running PVP and strikes. You do need to do the entire HoW storyline to get into POE unfortunately, on the plus side doing all the story quests at 32 gives you a ton of XP for armor.