@Davlamin Hey, these are all truisms of Arena but you're right in pointing them out. Just a quick summary of what issues still exist and some of the ways they've been dealt with.
1. This is a personal gripe of mine, luckily the issue only becomes apparent in tournament play, otherwise it is up to the disclosure of the combatants if they agree to combat with an incompatible character. So far the work arounds tend to involve a middle ground being found, which revolves around the balancing elements of T1 Eden era and some practical reductions of firearms and other long range high capcity weaponry.
This issue very much still exists, but its mitigated somewhat by these factors. Segregation based on tech level would only really be useful as a stipulation for tournaments, which is also up to the tournament host.
2. This is common, ultimately though it does not matter, you're in control of your characters actions, so all that a mastery of a skill entails is the ability by which your character carries out the action you intend, and the range of actions you can have your character make. If you yourself have made a clear error, overextending or fucking up spacing or some other common mistake, you've just made your supposed masterful character look bad, and will be punished. It's worth learning about close quarters combat or at least doing some online research before slapping that description onto a character.
There will always be issues in regards to the subjectivity of language, though a decent mitigating factor is a judge ruling or communicating with your opponent throughout the fight to ensure you're both imagining the scene properly. A recent example of this was LeeRoy and me fighting in our Heavy Hitters battle, where it descended into a slightly messy grapple, we ensured that both of us knew what was going on and cut off the potential for misunderstandings. It's not the only way to deal with this issue, but it helps.
Hope these prevailing issues don't put you off Arena fighting, there's still a lot of fun to be had in combat.