Its so damn simple that Discipline Priest is one of worst possible choices for Val.
We have raid with 2 healers - Holy Paladin and Discipline Priest. 1st possiblity is Holy Paladin got Val and Priest have some other weapon and 2nd possiblity is that Holy pala got some other weapon and Disci got Val.
1st possibility - Holy Paladin gonna put on HIGHER than priest Valnyr procs due to better healing and Priest gonna put anyway 30% absorb shield on tank anyway and PWS anyway Valnyr wont improve it at all.
2nd possbility - Holy Paladin will only heal and Priest gonna do LESS heals and that means he gonna make less absorbing Valnyr shield + he still gonna do their PWS and Absord shield from Devine Aegis so Basicly what u prefer:
15% of Holy Paladin Heals as Valnyr procs or 15% heals of Discipline Priest as Valnyr Procs.
So coming to conclusion is basicly
Holy Paladin have better HEALS or Discipline Priest have better HEALS (not absorbs)]
Holy Paladin won. (and all other healers aswell)
I was wondering Beacon of Light aswell gives shield from Valnyr?