Playing tank just feels like cheating. You just win because your team doesn't have 4 dps players and if you are a tank main odds are you are going up against some poor fucker who had to fill tank and will crash out when you outplay him blaming his healers and DPS. Also it drastically increases your chances of having 2 tanks so you get a normal team comp for a free win.
Tank however gets kinda stale, I have more fun losing as DPS than playing tank sometimes