I recently geared up for random BGs as holy paladin. I went with crafted plate set(could make it myself so it was cheap) and the rest was my dps pieces; trinkets, cloak, ring(1 crafted healing ring from JC), boots. I replaced them as I got enough honor for one piece. Remember that you are under geared, so you will be targeted often and thus die a lot. Honor gain per hour depends on whether you win or not. If you have any friends to play with, it could make things easier.
As for viability, every healer in a random BG helps, even when you are trained. In 1 vs 1(or small 10 man BGs) you will not survive for long, bar the bubble CD. In big BGs like AV you will be survive easier.