I played a ton of reaper all over tyria this weekend, and I played a few different builds. I thought that it was weird and clunky to start with, I would constantly overshoot deaths charge, scratch my own back with those claws and I would cancel my nightfall by running. But as the weekend went on I adapted my gameplay I learnt the enemies animations and skills and knew when to use my longer cast skills and when to pop stability, I would judge the distance between my and the enemy, I would back peddle to get deaths charge just right. I found playing reaper in verdant brink has made me a better player.
As for build stuff reaper makes a solid 3rd line for most builds, I always found that necro has 2 solid line to go into a build and then a 3rd that you can change depending on what you are doing.
Condi reaper is good it has some fun aspects but greatsword I didn’t see having a place on it, but reaper shroud was good for condi and it give you a stun and a leap that condi necro never had, and then there is the extra chill damage to add to dps but the internal cooldown on chilling darkness is a bit sad.
Power reaper is a lot of fun especially when you adjust your play style to it and don’t play full bezerker it is ok but not great or needed. I played half soldiers, half bezerkers and it was great, I don’t think it was optimal but it gave you good enough defense and power. The greatsword is good long cast times are fine, I’m used to it most necro skills have long cast time but now there is a ton of stability to use. I found zerging in wvw fun and very rewarding with greatsword and dagger/warhorn, I would play frontline, self stack 25 stacks of might had good stability, and I could still well bomb. Then playing in verdant brink I would purposely aggro extra mobs just for “You are all weaklings!” and well bomb my enemies to get 25 stacks of might in no time. I had no problem with cast times or cooldowns, there is little burst on the greatsword but if you use wells and “You are all weaklings!” then you have fast damage. Much like most necro stuff it is geared but to fight 5 enemies at once which it does great. I did also take this necro to world boss an some bosses were a lot harder too hit than others but I found the mega destroyer fun running out into the lava fighting it and then darting back with deaths charge, it was not efficient or even had good dps doing it but it was fun.
I even tried out Minionmaster a bit which was pretty fun and gave you so many minions, but mostly has the cool fact that you get reapershroud.
In short reaper is very fun, it does change the way you play necro. It does fill some gaps and does feel powerful but not overpowered. I actually felt faster and had to play faster when playing it. I think that it is great and that doesn’t really need much change, and deaths charge or grasping darkness does not to be targeted or ground targeted for when you get used to how they work they are great.