One of the key things in role-play and indeed any storytelling is maintaining the audience's "suspension of disbelief". This is perhaps all the more difficult when you yourself are part of the "audience". Suspension of disbelief is where an audience is willing to overlook certain aspects in order to be entertained. We as players of online computer games overlook many obviously unrealistic things in order to immerse ourselves in the story. Some of these are limitations with computer gaming - non-realistic graphics and sound, clunky keyboard/mouse interface etc. Others are inherent in the genre of fantasy - elves, trolls, dragons not being things we can experience in our real lives.
As players of an online fantasy game, we willingly suspend our disbelief in these things to take part in an enjoyable experience. Familiarity with other fantasy stories and movies means that we are unsurprised at non-human races, that dragons exist and can fly, or that magic has practical applications. All these are accepted as part of the new "world" we are involved in.
Where things break down however is the introduction of something well beyond our newly accepted framework. Instanced dungeons is one of the main "belief suspenders" in WoW and similar games.
How do you rationalise the "fact" that Ragefire Chasm and Stockades, instanced dungeons in the main Horde and Alliance capitals, are STILL full of hostiles, more than 5 years after WoW's release? Surely someone would have cleared them out by now?
How can my rogue claim to have cleared the place, and have an achievement to prove it, yet your priest also make the same statement, at a different time?
As you can see, issues like these can make or break your immersion into the story. There are a fair number of these issues imposed on us because of the nature of online computer gaming.
(not finished, but published so I embarrass myself into working on it later!)