The supposed handicap of the Advent Illuminator requiring 3 Hostility Labs (and associated reserach costs) can be mitigated by the Illuminator's high damage output, which can be attributed to its three beam emitters. Illuminators have a fairly good DPS/cost ratio, and when you consider your alternatives, LFs are, like you've already mentioned, too easily killed, flaks aren't that effective in frigate-to-frigate combat, and Aerias are prohibitively expensive (in terms of both credit and resource cost and fleet supply cost).

You definitely want a steady and reliable supply of credits and resources before you can consider building Aerias (since these guys cost 1200ish credits, 230 metal, and 220 crystal), although you get a quick strike craft advantage early on.

The cost doesnt seem prohibitive to me because the superior strike craft  make for a nasty surprise on anybody who didnt properly prepare for them.  Although i dont play multiplayer just against the AI and the AI doesnt prpeare and effective counter until i already have illuminators.

carrier is worth it, but will often provoke spamming of Flaks in response so be careful. you may need to supplement the carrier with some Disciples if that happens. if your opponent isnt doing a good job of scouting you you can bait and switch him too. show him the carrier and hope he builds lights and flaks in response to defend. then tech up to Illums and own him.