@Darth
My Scarlet ended the game with 4 skills completely maxed out, and several others at 3 or 4.
My Roderick ended the game with 3 skills maxed, 2 others at 4, and a couple random points scattered.
My Jahan ended with 4 skills maxed (including crafting and blacksmithing at rank 6, for shits and giggles) and also 8 spare skill points that I never bothered spending
My Madora ended with 3 skills maxed, a few more at rank 3, and 5 unspent skill points.
I would say that you could easily master at least 4 skills by endgame. 5 if you spent your points carefully. 6 if you abuse the Seller of Secrets books.
Why should you be able to master 7 skills per person? Because there are 28 skills? Why should you be able to master all of the skills in the game in a single play through?
Yeah, that happens when you buy the booster books from the seller of secrets several times over. But that's been patched though it still works in the worlds of older characters created before the patch. Otherwise you legitimately can only get two books that give three points each and even if both are given to the same character it's still impossible to max a 4th skill at level 20 with that character. Actually you'd be 5 points short of maxing a 4th skill so it'd also be impossible at level 21.