Jefe Bergenstein
Legend
I'll add my vote to yes, as its thematically appropriate and not overpowered. Moreover, its a "closing move" as opposed to an opening nova, as the additional benefit is healing you, which is wasted if you aren't hurt.
I believe the synergy is obviously an unintended one, and as a result I would not allow the extra damage from Death Touch to count towards the healing from Vampiric Touch. It doesn't nerf anything; you still get tons of necrotic damage, and you still regain (3d6)/2 back.
(but obviously, play what you like)