I was also thinking that the hero might be leveled up in a suboptimal way.

In attack, you definitely need to get “Magic of Speed,” and the sooner, the better. “Fire Arrows” is the most useless perk from this branch for Varens. Everything else is chosen depending on the skills taken. In “defense,” tactics or archery are good. If there is leadership, then “Retribution” is preferable. It’s not necessary to put points into “Readiness” for this hero at all. For Varens, the best defense is offense. The more attacks his troops inflict, the greater the chance of stunning the enemy. This means they shouldn't stand still. From the defense branch, it is more important to have Initiative (especially with “Tactics”) or at least “Stone Skin.”
I like to take Leadership - "Empathy" rather than Defense for Varens. You can see what happens (my replays from the Unicorn Empire campaign, but the hero leveling is the same)