My views taken from ~5 months (recently quit due to PvPatch 1.4) on a normal realm with characters of both factions, including a 60 shaman, with a lowbie character on a PvP realm and none on an RP realm - note that I also played EQ1 for years, and speak about what i know, ie. end-game content at the level cap. My views may not hold true for lower levels and such.
- The general playerbase is less mature than EQ1's before I quit that game, though it should be noted that due to game changes and customer treatment from Sony, the maturity level in EQ1 was going downhill fast.
- Competence and maturity don't necessarily go hand in hand, but there's a high correlation. Further, it's easier to forgive someone who says "Sorry, my fault" than someone who says "Lololo 2 wut b plz", or worse, blames others for their mistake - even if the mistake is the same in both situations.
- The horde tends to have more mature & competent players than the alliance
- As with other MMORPGs, there are far more mature & competent players on normal realms in comparison to PvP realms, can't speak for RP.
- As with other MMORPGs, the purest healing class tends to attract the most mature & competent players.
- Healing in WoW is highly tiered; shamans don't hold a candle to druids in healing, who in turn don't hold a candle to priests.
Try to view this in shades of gray rather than black & white; I've commented on general trends, and haven't claimed any to be hard & fast rules.