I tried this in season 4. I had 3 brutal elemental pieces, and 2 merciless healing pieces for extra resilience. I was about 500 resi. I also had most of the guardian healing pieces. So it safe to say my gear was allmost maxed out for this

It didnt work out by a longshot. It sounds fun in theory, but even with resto spec you will be slayed fairly quickly. To heal efficient enough to last a long time requires a lot more micro than you can handle in an arena as a boxer.