In response to what you said about no rep from instances...

I know that there is a system where you wear a reputations tabard and then when youre in ANY instance it gives you rep... but its not for all factions. Let me try to find a link about it, i think it was called champion or something like that.

Found it, source: http://wotlkwiki.info/index.php/Championing
Guess its only for level 80 dungeons though.

"Championing" is a system for earning Faction reputation for certain Northrend-based Factions.
The system makes use of Tabards available from certain Factions at Friendly reputation. By wearing a Faction's Tabard, one gains the Champion buff for that specific Faction and can then gain reputation for kills in any level 80 Dungeon, regardless of the Dungeon's native reputation.
For example, if a player wears the Tabard of the Kirin Tor in Utgarde Pinnacle (or any other level 80 Dungeon), each kill will grant Kirin Tor rep.

Currently only four major Neutral Factions in Northrend can be Championed: