I have to agree with Lav, Dundee. Once you start running instances things like holding aggro and generating threat are so important, whether you are RPing or not. Unless you're with a similar casual group who doesn't care if you wipe or not, it's very much suggested you get some tools to aid you in your roleplaying. The tools/addons do not detract from the gaming experience as you can incorporate your behaviour changes into your roleplaying (eg when you lose threat you can say "dear friends, please hold back your attacks for a moment!" or something like that).
You can kind of get away with it up until level 50 or so, then when you go into the bigger Old World raids like UBRS or something you will likely be paired with guys who want to level up to 60 as quick as they can so they can get access to Outland through the Dark Portal, and will not appreciate having to play 20g+ for repairs due to constant wipes. Wipes do cost money and they annoy people. The problem is at the higher levels, you can get one or two shotted by bosses, even if you are tank spec. As a tank you're a central part of the group/raid - if other dps die the group may yet succeed, but if the tank or healer/s die you're pretty much screwed.
Addons don't make it ez-mode - they just make you more efficient. For example, Quest Helper just tells you which general direction to go (like Oblivion if you've played that). Recount, if you're not planning to analyse your healing or DPS performance you probably don't need. X=Perl - if nothing else it will make your UI way prettier and more dynamic. And Auctioneer will basically do all the stuff you are doing manually, automatically. It will save you up to 2 1/2 hours worth of time in the AH each week - time you can use to run instances, meet new people, etc. Many casual players use add-ons to improving their gaming experience. Think of it that way.
