To begin when I first started the option of manually controlling your movement and skill output for the arena allowed you to climb ranks, as well as the auto option. Around the time the 2nd server became available this seems to have changed, and if this was intentional I'd ask it to be mulled over about retracting such change.
While there may be other reasons in favor or against, I know from a personal standpoint the ranged AI seems to be rather lacking; unless all your skills are essentially within the same range (yea archers @_@). What I mean by this, is for example I have one account set-up that even though there was more then enough time to have used all 6 a few times, and have won somewhere along the line, this AI decided to sit and repeatedly spam the lightning bolt until it eventually died... Another, issue I have come across; regardless of what set-up is seemingly used, is that left-click skills are seemingly never used by the AI. This can't be argued as using what's best in the instant either, as for example what logic would there be not to use say storm shield against a tough opponent either on the outset, or at the very least while your experiencing a significant loss of life with more then enough mana left? There's also the argument for properly kiting when possibly; say for delayed skills, or at the very least to I don't know, not sit in the poison explosion pool for example when you have "jump" skills...
Expanding upon said poison mentioned above brings me to the next topic for consideration. This being in the balance of the trifecta skill selection currently listed in shop. Therein you have 2 area poison skills, one of which you even have a choice to use as more of a self-ring skill when mobbed, and then there's a minimally timed single target stun...Now the upgraded output is "fine" but as the stun timing never really seems to take off anywhere near significant juxtaposed to it's cooldown(even with using a reduction rune) this seems to make it rather obvious it's been given the short-end of the stick if you will. As a suggestion, I would put forth the idea of having said skill's hit-box become a circular type instead of a singular. Having this multi-target close range stun I believe would do well to adequately balance what it offers compared to the other two, without having to bother with advanced stun times; which seemingly would be the easier target of change, but could end up rather tricky preventing a possible repeated effect or overall stun-locking combination down the line. It also would then still be comparable to other melee skill offerings.
In regards to skills in general; while I've noted a broad interpretation was acknowledged, I've only found the issue of skills occasionally not working in dungeons in regards to many of those that are archer specific, and mainly only under a particular circumstance. This being when select targets are essentially within kissing distance of your character. I believe knowing this, might be of assistance; should it not already have been noted, so that what might actually fix the issue would be to slightly inwardly adjust the range of said skills; especially as given those that are archer specific or can even mostly be used without a weapon change aside from the elemental mines being used creatively, archer lacks any anti-encirclement skills apart from it's arrow rain.
^This brings up another small point I'd like to have considered. That being in the possible creation & implementation of a cross-bow subset; or otherwise single hand option for bows. While yes, you can change class with a brief weapon and skill change at any time, not having said single-hand option I believe puts the class specifics at a disadvantage.
How so you ask? Well given that there are dual-wield options for both mage(staff) and warrior(a few options) you can one hand each type of these and create a mage/warrior skill hybrid; of ANY of there type of skills, to be used at one time. While I do admit this would take a fair amount of work, it is a issue I do believe should be rectified for the good of the game.
There are a few other things I have noted at present, but will be waiting for a full translation in order to bring them up in-case there is some aspect of the issue I may be missing.
Having said that, I may add to this post before then if I find others. I also encourage other players to list similar findings that all together might not fit neatly elsewhere here as well, and hopefully rather then creating undo clutter they might be noted, addressed, and maybe even past on in a much less chaotic manner.