Illums are the best lrm against corvettes, i don't know what you guys are smoking but atleast when the corvettes bank around the illums will hit 270degrees rather than 100ish.
Also i'd say illums are a great choice due to the upgrade path for their weapons... though same can be said for other factions, but what i'm getting at is.. and i consider advent to be my specialist race.. i rarely upgrade plasma until late game, due to illums/bombers and most cap ships using beams.
Also, ultra late, t8 with maxed beam damage and then range, coupled with repulse you can keep the enemy out of range but still within your own. HCs imo cost too much, they have their place in the fleet, but only 10-20 with ruthlessness for the 1.5/s aoe damage.. it all adds up.. against 50 ships, that's just an extra 75/s.
Anyway Placing your illums without the enemy fleet and keeping them moving is always a good option depending on whats happening, a good opponent won't let you sit in the middle and will move his fleet according.. against vasari it actually gimps them due to such a low turn speed and fire arcs.
People mentioning corvettes.. When you're t3 advent.. corvettes really shouldnt be an issue now.. you keep your illums and flak together, let your discs go forward. Corvettes aren't an issue. You can even build your own to snipe his lrms. From personal experience illums have the better offence to corvettes when trying to snipe them in fleet battles, because the illums have a better time hitting corvs. Sure i'm repeating myself but it's just to make sure you guys are still reading.