It does scale a bit: CON by +1 every 7 levels and the others +1 at level 14 so by level 21 you have +2 FIN/INT/STR and +4 CON.
It is worth it as pre-buff though as it is 10% damage boost from level 14 (2 points) plus the extra constitution.
Is worth 1AP? Well if you have 4 characters each doing 10% extra damage for 3 turns then perhaps but I'm not sure I can't work that out. I think you get 108% return on your investment all things being equal (you spend 1AP to get 52AP of damage rather than 48) That would assume all characters only did damage and all did the same but it isn't terrible anyway - certainly after level 14.
Should it scale more? I don't know but I don't think so. If you got +4 to STR/INT/FIN everyone would be getting a 20% damage increase for 1AP which seems a bit much.
