If you keep winning, it isent still the right time to Tank.
Other thing is that If you have a strong team, tanking it is not so easy with 11 games remaining. The first time i Tank one of my teams i started on ROUND 14, i was 5th with no chances of top 4, only 7 points ahead of 8th, but only manage to be behind in ROUND 25.
Even playing with ilegal formation i still won 2 games and draw 1.

You Never won the CUP, If you Tank it Will be mutch more difucult to win it in the next seasons.