Heavily based off of Helel's build (Your text to link...) This is the build I currently use as a level 50 engineer without any elder gem enhancements yet.

I personally use this build and can attest to its effectiveness for holding agro.

Skill rotation is generally as follows>


Open
basic attack (right click target to perform)

dash, dash
Instant cast






Chorus
as soon as Volatility dips below 70 hit it to get the instant cast



As needed
for a spare taunt/interrupt, be advised you'll need to be careful with the bot because he generally is a dick and has little concern for your light armored team mates behind him that are about to get con.d in the face.
activate the bot prior to the fight, use the ability when your shields dip below 50% (not sure if this is optimal, but I use it as a rule of thumb for myself)

use this if you have unavoidable damage coming (particularly if you know that the wrong skill got interrupted early and you need to grin and bear it until interrupts are ready again)

When pesky dps does lots of dps and suddenly the mob realizes your dps is not that much dps

for when a lot of mobs suddenly realize the pesky dps is doing lots of dps and you're not. (or large cooldown taunt for you overly educated types who dislike colorful descriptions)