Why longswords have 0.225 lethality?

[Burebista]

As for the stat-balancing in EB, part of the problem is the R:TW engine. Lethality simply is far better than attack. Smiths and experience can raise attack and defence values very high even if they were low to begin with, whilst nothing changes lethality. Looking through the "Surprisingly good/bad units" thread this theme is apparent again and again. Units with high lethality are surprisingly good, with low lethality surprisingly bad.

Your theory fails miserably in multiplayer . it is true , high lethality helps , but the better stats that make a unit superior in multiplayer are size , Ap attribute , morale , shield , discipline , charge value and ofc price(there are more but these i consider more important than lethality).

By your assumption , a unit such as solduros or neitos might appear godly , but they are far from it. in front warfare lethality is crappy unless you get behind your enemy , and also in 1 on 1 i know a lot of units that beat solduros any day even with lower lethality. i personally consider from personal multiplayer experience that high lethality is weak vs high armour values or tightly packed units.

In Europa Barbarorum, the Legions would have a very big advantage if they switched to longswords. They'd become twice as effective killers. In reality, I expect this would actually have decreased their performance in most circumstances, which would then explain why they never did adopt them.
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No they wouldn't. High lethality in EB is usually compensated by a looser formation which makes the unit less effective . Romans used tightly packed units with short swords to mainly stab. the change to Spatha came after the discipline and formation of roman infantry had decayed so wielding a larger sword in a looser formation made more sense.

EB can't representate all the details , that is true , but all the units behave as they should so that is a great merit for the team. Even the multiplayer is balanced (excepty that damn guard mode issue)