I also agree to this.
But imho this is not a bugged class or is not "OP". The K/M has always been a magical tank basically - resp. it was the idea of that.
But now it's the same problem like the wd/w on off server has: People play a tank class with dps gear and find out that this matters a lot.
The problem we also always had in the past was that there is always a class that is stronger then others. For we have a two-class-system there is no possibility to balance everything on the ideal way.
On Off Server about 70% of all highs played R/M, Warmage or M/W. And on Arcadia these classes have been replaced by K/M, S/Wd and such (excluded Warmage; this one always deals a strong dmg).
However I agree that K/M maybe is a bit too strong. But I also analyzed that other classes like druid/rogue or even warlock/champ "CAN" make up their leeways with a great gear.
For K/M you need nothing but about 80k Matt, the tikal sword and maybe a setbounty for more crit-dmg.
The reason why this is enough is that HOS HM has a Mdeff cap at ~80k. That means you don't need more than 80k Matt to deal your Max-DMG. (Same dmg you deal on Lv 1 mobs).
And K/M has the highest base dmg ingame so once you reach the cap you'll be the dmg-god.
But in other instances like CL or even non-custom Inis like CoE the K/M is unusable. He has no chance of increasing his Matt but only dmg. With a more or less "good" gear, the average K/M stands with about 400k Matt in burst. GoH e.g. has a mdeff cap of 480k Matt. So you see even in this old easy istance the K/M is useless.
To come back to topic I would suggest not to crash the K/M by nerfing some skills/buffs but to increase some bosses Mdeff.
The result of that "fix" would be that some guilds need much more time to finish one single HOS run but to play more tactics. Maybe afterwards the 6th boss has to be nerfed because there is much dmg left to kill the horse on time, but this is another story.
To summarize: Yes, the balancing has to change to some classes. 
