I'm in January 2000 and I've been using power armor for a while (I rushed elerium batteries in an attempt to get gauss weapons, but still haven't gotten any aliens to reveal the secrets of antimatter containment. Elerium battery's prereqs did get me mass drivers and lasers, though, which is nice). I don't really think power armor needs to be nerfed - at $750,000 a suit, you're spending a significant chunk of your budget to outfit entire squads with it, and it's destroyed completely when an agent wearing it dies, so you have to buy it all over again. Plasma weapons, such as even sectoids have in early 1999, have a fair chance to penetrate and deal fatal wounds or even outright kill agents. Power armor definitely helps protect your best agents, but it isn't a miracle armor, and by buying it you sacrifice whatever facilities you could have built with that money instead. Plus you also sacrifice the backpack slots too, which means you can't really carry multiple two handed weapons (and have to run back to the vehicle to swap to a different one), or much extra ammo for weapons with bulky ammo, like the taser cannon, which I'm still using in January 2000. And you can't crouch, so you lose the aim bonus and lowered chance to be shot from that.
Power armor has made all my underwater missions trivial, though, but I haven't progressed them very far - I've been more focused on the space aliens and shogg etc since they seem like greater threats. The sonic weapons I've seen so far just have a near-zero (but not quite zero, I've had agents take damage a few times from lucky shots) chance to do damage to someone in power armor. And gunpowder weapons also don't do anything against it. Maybe if syndicate had better ones. I haven't done the math but I wonder if the asuka 4000 could penetrate it. Gauss weapons can definitely penetrate it, but that's no surprise, given how powerful those are.
I'm willing to pay the premium for power armor because I'm trying to keep as many agents as possible alive, and because the council of funding nations has been throwing money at me hand over fist since mid-1999 or so. When I first got power armor, though, I couldn't afford more than one or two suits a month, and that used much of my budget at the time.
Oh, and as an experiment, earlier this year IRL, I tried sending power armored agents to try to melee a vampire knight. The vampire knight cuts through power armor like a hot chainsaw through butter. So project "capture a vampire knight with stun spears" was a no-go, lol.
Iirc I shut the cults down before I got power armor, except possibly for the one I left for last (the American one, EXALT), and I think I only had two or three suits of it on their final mission? I had most of my troops in heavy tactical suits or heavy tritanium suits for most of the cult campaigns, once I had the tech (I couldn't always afford to keep everyone outfitted with them).
But also I got lucky and captured a landed UFO in 1998, which provided a huge boost to my research efforts. And iirc I shut the cults down by December 1998, with the possible exception of EXALT. I don't remember if I finished them off in late December or early January.
If anyone is wondering my current tech level, as indicated by what equipment I'm bringing to missions: Depending on the mission, my agents use taser cannons, laser rifles, asuka 4000s, occasionally a couple var assault cannons, or stun spears (for syndicate, osiron, or the new ghosts). Also tritanium handcuffs, medi-kits, advanced healing sprays (for self-healing), emp grenades for indoors turrets. For really difficult things, I bring gauss rifles or pistols, but I haven't unlocked the techs to manufacture my own or to make more ammo for them, so I use them sparingly since I only have what I've captured. I've got Natasha's custom sniper rifle too, of course, which does an incredible amount of damage in the hands of an expert sharpshooter.
