I've been reading up about it but I don't really "get" what i'm meant to do at L85?
Back in vanilla days it meant starting getting your Tier 0 set together by running 5-mans (Strat/Scholo/BRS/DM) and then taking on Molten Core. But there doesn't seem to be 5-man sets in Cataclysm?
Should I bother finishing all the Cataclysm questing areas or just stop at L85?
And I don't get all this "points" system for loot - is that just for raiding, for 5-mans, or both? And something about itemlevels?
The whole thing seems like complication for complication's sake. What happened to the days of WoW being straightforward?
At level 85, I would suggest working on getting the required item level to be able to do heroics (329). You can find this in your character tab at the top. This would either be doing regular dungeons or working on getting exalted with the factions to buy some of the blue and epic gear. After you are friendly with the factions, you can buy a tabard that you equip. You earn reputation from killing enemies in Heroics and i think the level 85 dungeons.
Once you have 329 item level, you can queue for Cata heroics. Then just spam them until you get enough item level to queue for LFR (looking for raid). I think its around 370.
The way the point system works is:
Justice points are earnt from Regular dungeons when doing the looking for group. When you complete a dungeon with that, you get 125 or something justice points. This effectively buys the last tiers items that were originally from the valor points. You also earn them when killing any boss in any heroic.
You then have Valor points. These buy the "current" set of items. They are at the same item level as the current raid content. You earn this by completing heroics in the Looking for Group tool. You also earn it from boss kills in raids and completing the LFR tool.
Regarding item levels, they have always existed in the game, but only really mattered now. Basically, as new content is released, gear has a higher item level. Its basically how many total stats it has. They have changed it now so when using the LFG/LFR, you need a minimum item level to join.