I'd recommend a burst cannon over a hyperblaster, with ammochain. The more rounds you get out per burst, the better, or at least that's what I found. I had a (to me) very impressive damage output with my F2N1S2 laser rifle - massive accuracy, 11 rounds per burst (with 2TH), and a regenerating ammo supply. I realize those mods aren't easy to get, of course, and it took me the better part of an AAo666 run to put that together.
T3A1S1 sounds like a pretty good combination, since the fire time reduction from the tech mods is very useful for getting off a lot of bursts before enemies can react. Still, I'd rather put it on a laser rifle then a plasma rifle, if you have the chance - especially if you're using rarer modpacks like S or F that might not show up again in an Ao100.
A nuclear plasma rifle is also a good option, since it means you can disregard looking for and carrying around ammunition, especially with a MAc build. A laser rifle with an N mod will give you 40 bursts in a row before you have to wait for it to recharge, but a nuclear plasma will still give 24, which is a pretty significant amount as well - it just may not be enough on Nightmare.
Speaking of Nightmare, I can barely get past the Phobos base on that setting, so take my input with a sizeable grain of salt. I just know what worked for me on my Ao100 games, and that may not be the best setup even for HNTR, much less N!.