At its core, kensai was meant to represent a trade-off: a warrior that rejects magic and instead hones martial prowess. In practice, this meant giving up the use of magical consumables in exchange for passive, constant buffs.
A secondary design philosophy can be found in its appeal. Kensai were originally designed for players who preferred more casual play, who didn't want to track potions, wands, spell effects and instead focus on other things.
Somewhere along the way, the path lost sight of both ideas. The current kensai boons are powerful because they stack effectively with key potion buffs and planned gearing. Kensai are no longer the realm of the casual player trying out the game, but are instead picked up by players of all skill levels - many experienced players consider it a mandatory element in certain top 'builds' and character archetypes.
The fact that the path is currently overtuned isn't necessarily a deal-breaker; classes and paths that are too powerful can be brought back in line with well-considered balance tweaks. The issues were with the path itself, namely: 1) Kensai no longer fit its concept either mechanically or thematically, and 2) the core philosophies of the path posed intractable problems.
The second point merits elaboration. The core trade-off of kensai was giving up magical items (first all magical consumables but later just UMD trinkets) in exchange for passive buffs. This is problematic since it defines the power level of the kensai relative to other melee builds based on how useful or mandatory the server's magical consumables are.
The state of kensai became synonymous with the state of UMD. As melee classes became less and less dependent on UMD-based scrolls, kensai became all the more logical (perhaps mandatory) for fighter types. Similarly, the addition of powerful potions would benefit kensai most of all. Both factors had to be considered in all spell changes or crafting additions, limiting what the staff could do with consumables.
Furthermore, experience shows that a 'casual play' class leads to flawed outcomes. Either the end result is a path that is weaker overall, in which case it is regarded as a 'trap class' that might disillusion new players who were led into a dead end, or the path becomes an overly powerful tool that can be used by casual players but is more often employed by more experienced players to upend the power curve.
Even if the proper balance is found, the casual-play path will enjoy innate advantages due to ease of execution being advantageous in PvP and high-pressure situations.
Ultimately, we decided that the core vision of the path was lost along the way, and its current dynamics were unhealthy and unworkable. The path will therefore be phased out.
Kensai will no longer be selectable as a path. Some of the kensai's passive boons, namely saving throws and detection bonuses, will be removed to bring the path's power level in line, but otherwise existing kensai characters can continue to play as usual.
tl;dr: The existence of kensai posed continuous and difficult problems for server balance and development. Kensai will no longer be a selectable path. While existing kensai characters will lose some passive buffs, they can continue to play as legacy characters.
