6 seconds is two halberdier attacks, which means that the unit would tank 8 hits against halbs if they attack one at a time, only 7 against two halbs at the same time, which is only one more than Franks
For a UU made in the castle thats worse against arrows than paladins and just as expensive thats not too OP
Or maybe it could still be slow to recharge but be able to accumulate two hits instead of one
The new Three Kingdoms civs seem very overpowered to me, mainly because they are both fairly strong in early game and have some pretty insane late game buffs.
The Hei Guang seems like a knight thats just a bit better in general but weaker against its counters because of lower HP. Its not as good as paladins, but better than Cavaliers
The traction treb seems really really really good. Its a bombard cannon without needing chemistry, with higher range and good damage
The Shu seem the most OP to me funnily enough, despite their tech tree being the most limited. They have a really solid eco bonus (almost as good as the Slavic bonus but kicks off earlier) and then that food can be used to get discounted techs for your main unit, then in late game you can get the best archers in the game with the UT. And if that wasnt enough they have bonuses for infantry and siege and good UUs,
The Wei I can see being very OP, but they are somewhat fragile like Burgundians. They can outeco the Bengalis very quickly if they take the mining camp techs with an strong military bonus in mid game (Hei Guang is slightly better than knights), their UU is super good too. In late game their cav is weird, the Tiger cav is just super tanky, while their knights turn into budget boyars with barely worse stats in anything but pierce armour. Their trebs are cheap, which is nice. They just seem way too well rounded before imp and even in imp their cheap siege and still quite good units seem like too much
Their castle age UT pays off fairly quickly but its only like 4/5 more villagers.
The Wu are the less flashy of the bunch, but their early game is really dangerous. If you fully commit you can get a lot from their food bonus. Their military in the late game is ridiculously well rounded, but the only thing which may be actually super strong is their trebs.