I don't know if this is the case, but if PS:T is keeping to AD&D rules, raising proficiency should affect THAC0; having NO proficiency results in a penalty, 1 proficiency means no change, 2 proficiency gives -1 THAC0, and 3-5 all reduce THAC0 by an additional -2 (so -3 total). So you definitely don't want to just stop at 2 points for that extra 1/2 attack--go all the way to 3 at least, even for your mage.
As a fighter, you may also want to consider whether, instead of using 2 points to boost 1 weapon to 5 (so you get an additional 1/2 attack for that one type), you might want to spread the points out and have 3 weapon types at 3, giving you access to a wider range of weapons and damage types (so you could have a slashing, a piercing, and a crushing weapon).
And bumping from 3 to just 4 stars is, as far as I can tell, absolutely useless--either go all the way to 5, or just sit at 3.