The GI event is a pain but it's definitely not the hardest event in the game. At least not in my experience - I guess that's a bit subjective so YMMV.
The assault battle difficulty is consistent with other assault battles. I have guild mates that have done CT3 without Reva - we don't have her unlocked yet. It comes down to getting enough stacks of the event buff and timing your heals correctly. I haven't done it myself because I don't have the patience for it - but eventually I'll get tired of missing the rewards and I'll get it done. You only have to do it perfectly one time, then you never have to do it again. The same is true for the GI unlock.
Inqs are a great team and they have been since GI came out. The way I see it, they've got two strikes against them - there's still a lot of negative sentiment because of how heavily CG pushed them. I feel like that's a shame because they went out of their way to warn us ahead of time of how much they would be needed (which was a previously unheard of level of communication from them). The other strike is that their kits are all so heavily intertwined and dependent on the purge mechanic that they're a tricky team to really learn how to use well.
GI with one or more of his omis is more than capable of taking apart a JML team in TW. Outside of TW it's still possible, just has a lower success rate. They've been known to take out JMK/CAT teams, though I wouldn't try that myself. Without CAT they'll destroy a JMK team though. That's not to mention other Jedi teams and teams that dispel purge often. They're a virtual swiss army knife with tons of tools at their disposal. If you mod them well and learn how to use them, they're an amazing asset - even without Reva. With Reva they're just stupidly powerful.
I really don't know why the unlock event is so frustrating. It's not like people are going to do all the work of farming and relicing the requirements without doing the thing - so it doesn't make a lot of sense to make the thing frustrating. That's how it's been for lots of strong characters though so I guess it's not off-script. Good luck - hope you get through it OP.