I'm not sure if I have the time investment that I used to when I played WoW to be able to find a guild and set time every week to do a raid in this game. Also, I'm not sure how operations compare to WoW raids in that you need to know the fights in and out and that pugging could and usually would lead to a ton of wipes and require a long time to complete.
Nope, they're very easy tactics-wise on a normal/pug difficulty. Think of a first-tier WoW raids (Onixia/Molten Core etc). On a hardmode/nightmare they require really good healing/dps although still remain very simple in tactics.
Since this is the case I wanted to just find 3 other dedicated "casual" players and just do hard mode Flashpoints instead. Is this idea viable? Would you be able to just straight into hard mode fresh from hitting 50? Or after buying whatever gear you can from commendations and GTN? Or is the progression:
Operation > Hard mode FP > Hard mode Operation > Nightmare Operation
Yeah, flashpoints are real fun, but they might not be very friendly to a fresh 50. You absolutely need to buy anything you can get on a GTN and prolly should do the dailes on Ilum/Belsavis for some more mods/barrels. Plus you should probably do the pvp dailies for champion bags which can contain pvp set items with lvl 56 mods - really useful. Normal mode operations are alot easier then HM FPs though. And if you can, you should probably do them aswell because its basicly a free loot. And remember to do the pve daily/weekly quests to gear up faster.
The progression you described is pretty much it. Although you can start with HM FPs if you group is geared with craft/GTN items/mods and know what they're doing
Also, is it possible to still gear up for endgame with only hard mode FPs? I'm not sure how many tiers of armor there are but for example, would you still be able to get tier 1 or 2 out of 3 from just hard mode FPs?
Yep. Pretty much. You get 4pc t2 set (which comes with lvl 56 mods in it) + some random epics with lvl 51 mods. For comparsion: normal raid bosses drop the same tokens (t2) which final HM FP bosses drop. So you can gear up in HM FPs and jump straight to HM Ops (although someone in you group still needs to complete the normal mode to switch it to HM