An optimal single target attack chain is just that.
It doesn't mean don't use Burst or Focused Burst. It means, here how you kill stuff faster when Burst is recharging or you're down to 1 or 2 enemies since you brought up some key complaints of general slowness. By all means, you should absolutely be using Burst during AOE situations- it's one of the best melee AoEs in the game since the Stalker version has 100% (instead of 50%) chance to crit from Hide. Likewise for Focused Burst when you can take advantage of the ranged component.
Sorry if the advice sounded rigid! I only meant to address your original complaints of slowness in one of the fastest melee sets in the game.
Opportunity and build freedom comes in different forms! I personally played 1-50 twice on original live and HC with a KM/EnA Stalker and I found the lvl 32 power to be extremely lacking after taking it both times. A near 3 second long attack (that doesn't crit) felt absolutely shackling and I was glad to be rid of it. Plus dropping Concentrated Strike frees you up of more power pool picks. I discovered it for myself (then found others did too) and it really didn't feel cookie cutter to be honest, felt the opposite since I broke past the game's prescribed method. It depends on how you look at it!
Absolutely feel free to try out the lvl 32 power and all KM has to offer and reach your own conclusion.