Your math is off. By a zero.

Example:

Quote Originally Posted by DracotheDragon View Post
Consecutive wins to get fenrir 400,000 (1 million / 25 sticking to the after win bonus)
1 million divided by 25 isn't 400,000. It's 40,000.

You seem to make the same error through the rest of your math too.

So to redo your math, let's say that you have someone intentionally losing to you in TT to help you farm, 25 MGP per match. If they're intentionally losing, you can work out where to place cards every match for you to win, so no thinking on turns, just click and drag. Let's estimate 3 seconds per turn and 3 seconds to start matches. 30 seconds per match works out to just under 14 days non-stop, 28 days in 12-hour periods.

Again, however, this is only playing cards against another player who's intentionally losing to you. It's ignoring any other potential gains like cactpot or GATEs, and is obviously going to take longer than if you could beat NPCs who give you far more MGP per win.