As you observed, melee builds are tough to level compared to casters (AAR arcanists are not overpowered, they kind of suck in the end actually) -- you'll have an easier time maxing out one or two good ranged skills and just nuking everything in Veteran until you can get good enough equipment/enough skill points to make the melee side a bit stronger. As a necro, Ravenous Earth is a good choice for this purpose. You can then respec into your proper build once you're ready. Also, if you're aiming for a vit damage melee build, your best possible weapons are probably going to be MIs, unfortunately.
In terms of long-term advice for your build, I'd suggest a few things: more Pneumatic Burst; Blade Barrier as a ohshit button; Anatomy of Murder is generally p. good; as is the Nightblade debuff aura. You might want to minimize your skillpoint investment in the DW WPS skills (except for Whirling Death, which is quite good) in order to have more points to toss into more useful stuff. Bone Harvest is indeed very good for a vitality-focused melee build, and you should max it + soul harvest asap. Unless you really want Execution (hint: you don't) you should stop putting points into Nightblade and focus on Necro so you can grab Harbinger of Souls later. Make sure you max spectral wrath (and ideally get some other means of giving -resist) before you get to Ultimate or you'll have a rough time with certain enemies.
I meant AAR Arcanists are op at leveling, not at endgame, I know AAR has the disadvantage of not having any life leech. I'll get rid of most of the points in the DW techniques and get Whirling Death and Soul Harvest asap. Perhaps this is my end-game build ->
https://www.grimtools.com/calc/vNQJ3YR2 I got rid of most of the DW techniques and got Harbinger of Souls. Also notice how I got the summoning constellations cause I think it's going to be cool, and that's why I also have Blade Spirit. Perhaps I can remove points from Phantasmal Armor and put them in either Shadow Dance or Anatomy of Murder. Check out the Chillwhisper set I equipped, I was hoping they'd put a vitality/cold set in FG and they indeed did that.
EDIT: After shuffling around some points, I managed to get to Crucible 70 at lvl 30, it's not bad for a melee build, but it was a very lucky run. Crucible gives a lot of experience btw, I'm not sure whether it doesn't give more than the main campaign itself, which is weird. I mostly played it for Devotion points, but I also casually gained 3 levels. The turn-in at 70 gave me a whole level of experience.
EDIT2: The twinking potential in this game is intense. Once I got to lvl 35, my damage almost tripled from Deathchill relic alone, I'm pretty sure the Reaper does more damage than the Arcanist now. I'm curious what will happen in Crucible, will try it out tomorrow. I also must commend Crate for being able to create a system where almost every skill is unique in itself and it crates potential for interesting builds *that play differently* and all are equally engaging. My main still remains my favorite, but I can't pick between the Reaper and Arcanist, which speaks volumes, and I feel like I haven't even scratched the surface. Obsidian, take note.