1. Disc and Pallies have naturally inflated numbers from absorbs
2. HPS meters can be inflated if people are taking avoidable damage
3. Rdruids are naturally prone to sniping, artificially reducing our HPS without necessarily reducing our value as a healer
Personal logs are more useful because they can actually be examined for spell usage (as Fleurs did for shamans on Garalon). They give real insight into which spells might need a buff, which might need a nerf, etc. It's not perfect, but neither is Raidbots.
I've never ranked on any fight as either rdruid or disc, but we still manage to kill dragons because we, as a raid group, are not taking too much unnecessary damage, and we, as a healing team, do what is necessary to keep people alive instead of simply trying to meter pad.
I'm also wondering, to be honest, why Raidbots/WoL even matter right now when we don't have any parses from 5.2 (and T15 fights for that matter), and when a large part of the problem with rdruids is playstyle/mechanics.
I guess what I'm trying to say is that if you want to really get into the numbers, you'll have to examine both Raidbots and WoL; you can't really draw any conclusions using just one.