Thanks, I'm working from
this build that was suggested to me.
PoB link.
It mentions enlighten, but only if Wrath is added (which pushes the reservation up even further). It also mentions The Devouring Diadem but only as a nice to have as opposed to a requirement.
I took a screen grab of the passives as I don't have a Windows PC available to check the PoB passive tree outside of the game (at home anyway). I'll trace the image in game later to see if any of those nodes also reduce the reservation cost.
I did notice there's a skill I'll pick up later called Mind over Matter which will help a little with my defences as I'm not getting much gear with life at the moment.
I'm generally getting on fine (just hit act 7). Clearing maps is pretty simple but bosses and some harder mobs are making me work for my loots!