I'd like to add a few thing here for the Eng's side
1. Suppression Usage in SY: When the boss pops-up and everyone is killing off the first wave; send a heal and rev (rev boosts mana regen by 1 while boosting hp when needed) this gives you enough time to run by the entrance and Suppress the next wave until the first one is done *make sure you face the right direction & your target is on the oncoming mob NOT the one on the oposite direction or it'll disturb the Op's and Comm's pushes*. Remember, the higher the level of the skill, the more you can suppress (i.e. distance & timing is also key) & the longer it'll last so make sure the boss and players aiming at him aren't near so you can use it. Then target pusher (lizard heads) & aggro him towards you while you try to ancher on a wall or move around to send heals out again.
2. Pain, Decay, & Wither: Great for bosses in general and all pushers (even the ones in Voleria and the snipers there). Pain ticks a certain amount, Decay is awesome because it slowly drains the HP of the selected target, & Wither does good dmg over time. Vital because it makes it easier & faster to kill off the main threats in mobs & once you get to the boss, spam them along with your heals to make him feel the pain.
3. Sonic Boom & Transference: Two good AoEs when used correctly. First off Trans helps heal you per dmg tick on a mob so hell yes, remember we Engs are a vital member of any raid! So an extra heal for yourself with a bonus of the skills AoE is great! Might not take out a lot of HP from the mobs (even at max lvl) but it does help. As for Sonic Boom, its great to use to help add dmg to a mob as your team mates use their pushes. A good example to this is after they stand up from a Comm using Stomp. Adds some nice dmg and helps push them farther. SB & Trans are also good after Suppression. Yes I know SB has a long CD but when used at the right moment, it can be very useful! It has saved me many times before (especially on solo runs!).
It takes some getting used to and mastering of your skills so of course use whatever you can at your level to suit your play style. However, sometimes you have to use skills you don't like and learn ways to use them to your advantage. I didn't like Suppression and Sonic Boom for a while but learned to use them to my advantage in a way that benefits everyone in my raids.
Hope this helps!