Look at it this way.
What 4.80 changes as opposite to 3.70?
Special of a hero should already be maxed by 3.70. What really changes is the stats - attack/def/hp.
So need to look at the special itself, what it does. Is the special oriented at stats of a caster? Or is it more oriented at stats or others, or completely independent?
Specials that deal damage (direct or over time) are tied to hero’s attack stat. The higher the attack the higher the damage. That’s especially crucial when it comes to snipers. That final ascensions brings them to entire new territory. It’s similar for AOE dmg dealers, but these are usually coming with another utility beside the damage. Sometimes they do not fall that much behind if they are only on 3.70.
Heroes stats also matter when you plan your defense team, especially tank. Final ascension gives boost to survivability that a lot of heroes need. Average tank at 4.80 will by principle perform much better than great tank at 3.70.
Buffers, healers they are all about the special, their job is ensure the other 4 guys in the team are strong. These skills are independent of stats at all. For Tarlak it’s even more so as even his heal is nominal and not % based, so even healing himself the value will be the same 3.70 vs 4.80 (if it was a direct heal, like Rigard, he’d be healing himself a bit more as % is hp based and his hp would be higher).
It is without saying that Kingston benefits from this final ascension a lot more significantly than Tarlak, with whom you will not feel basically any difference. Trust me on this.
Besides, Tarlak will be very sensitive to release of any new titan specialist hero. Miki is already much stronger than Tarlak, and his release made Tarlak from one of the most desired hero to a ‘meh’ category. We’ll definitely be seeing another hero oriented at buffing tile attack this way. Good sniper will always have their place in game, a specialist like Tarlak will lose any meaning if a stronger hero is pulled, even if they were just 10% stronger than him. And you are not getting your tonics back when this happens.