i thought about this.. also thought about converting my warlock to echoing strike but i didnt enjoy the way the skill felt and i hate his free "Blink"
If you are after runes it doesnt matter if you play Zon, Sin, Nec, Pal, Sorc, or Lock.
Only hork Barb is the move here.
Get as much % on Find item as you can (Warcry GC basically), with highest clearspeed (WW is rly nice, I ran like 6 or 7k with it and felt good), and you should get your rune faster, just because... roll item drops 2 times....