You raise some good points, so let me see if I can offer a few thoughts.
First, the War Hero relic is definitively better than the Matrix Cube, so if you can stomach the PVPing it's an outright upgrade. That being said, you could wear a Rakata set from the vendor and heal everything in the game, so if you don't want to PVP there's no massively compelling reason to force yourself.
So yes, as it stands, irrespective of your second relic choice, you're not going to have any issues with maintenance healing. And when you do hit a phase when the healing demands spike, for 30 seconds the Campaign relic will effectively be much more useful than having the War Hero version. It's just a shame than 1.3 reduced the efficacy of the relic at filling this role; 405 Power for 20 seconds was that much nicer.
Still, my experience on Kephess is largely similar; I never used the Campaign relic nor my Rakata Adrenal after progression attempts. On that basis, the War Hero relic is the more attractive pick, because if you're not using the clickie you might as well take the passive boost and give yourself more headroom in general.
This makes sense. Given that once you have gone pass the learning phase, there probably isn't going to be much use of the clickie relic since most of the damage would be rather predictable and you can plan ahead for them. I'll probably keep the clickie relic while we're still progressing through HM Kephess, and once we get that down, change to one of the PVP relics for the passive power boost.
I also want to comment on the build above and not going 3/3 in penetrating light or taking this point from Pain Bearer. I take the point from Valiance. My feeling is that the damage from Noble Sacrifice is something you regulate and plan for. You know when you can safely do this and heal up the damage (usually standing in salvation). I don't usually have a problem healing to full after a NS. With Pain Bearer, this helps in emergencies when I'm all of a sudden in threat of dying. The extra healing is essential just to keep myself alive. I just feel that the extra 1% crit chance is worth more than saving some health loss from NS when you almost never have any issues healing this damage anyway.
I agree with the point that usually when you use NS, you plan for it and healing back the damage is not an issue. I personally run with 2/2 Pain Bearer and 3/3 Penetrating Light with no points in Valiance and I don't have any issues. The decrease in health spent is kinda lack-lustre too at 2% per point, which amounts to 400hp if your max health is 20000 (the average amount you should be hitting in BH/campaign level gear).
Having said that, it still amounts to personal preference and I can understand wanting to take up Valiance to take smaller health hits so that you feel safer just in case you end up taking spike damage for whatever reasons.