1) I'm not stupid, please don't assume otherwise. Obviously I included the base -_-
2) We are talking about someone who don't have a grid at all and is trying to set up one quickly for the tower. We are obviously not talking about a 2 years veteran, here. Calculating which kind of skill should be leveled up first quickly doesn't apply to anyone "who has played for more than a couple of months". Other than that, I take a SR grid, not a R grid or something like that.
You are right on the eidolon attack, but it doesn't change much if you are also including a 100% eidolon in the calculation. The numbers will be a little bit more closer, but the results will be the same.