@reimangadex Based on how his offense skill is +26 from the same cards as the +26 Strength I think it's probably a typo. It was either supposed to be +2 Strength and +1 Defense, or +39 Strength and +8 Defense, otherwise it doesn't make sense for +2 offense x13 to be correct unless, there is an additional stat calculation that wasn't shown for some reason, like Defense+(bonus x0.75), which would explain it but would only work if it showed us it exists in the first place.
@OsoJr I assume that it's due to 2 things, first the lv cap being removed means he can get stronger forever, second being the cards giving bonus stats that stack, possible infinitely, which means that the bonus stats can more than compensate for the reduced gains from level ups. Say that a Hero gains +10 in each stat per lv and Summoner gets +2, if he collects enough cards he could have a bonus +50 to each per lv, which would more than make up for the slower increase in base stats, though that's assuming that other classes can't get bonus stats from passive skills or something. The difference is, easy fast stat gains or harder but more potential stat gains.