I actually encourage tanking because it is an effective strategy of playing T11, If your having a terrible season you are better off tanking and failing to promote. There is nothing really to be gained by finishing 5th, 6th or 7th, Especially if your on a server full of token buyers and you do not have the resources to compete.
Plus there is other reasons to tank a season rather than just having a bad season or faced with a tough league draw, You might just simply want to take time out from playing this game because TOP ELEVEN NEVER SLEEPS.