Rune Knight's have never been able to put up a fight with a sura, at least from what I've seen, and I've seen a lot. Though they did nerf the only skill that could effectively kill a sura in War of Emperium, Reflect Damage, even though that never worked with my Royal Guard:(. At least she can survive any one hit skill except for the occasional Guillotine Fist.
And supposedly Rune Knight's did get a buff to Ignition Break, though my Rune Knight does less damage at 138 with more str and atk than at 116 with a Claymore and about 80 str.
Crushing Strike says hi. They can kill any other class including other RKs with this cheap skill. Thank god it's not spammable tho.