First and most importantly stop using SMALL groups of minions, start using BIG groups. By far the best personal scale tank is a squad of 10+ Stormtroopers, and I mean by far. That's a wound pool of 50+ wounds, soaking 5 every hit. So your players 4 hits at 13 damage just barely managed to take out 3 of them... Guess what, their dice pool is still their peak AAPPP! It would take 2 solid attacks to bring them down to where most GM's start their Minion groups
A Nemesis is typically a glass cannon, just like most PC's they hit hard but go down super easy. You need to make them hard to get to and hard to hit.
There are serious consequences for using Auto-Fire on a regular basis, the authorities take a very unfavourable view of them and tend to give people carrying them a very hard time... Just saying.
Edit: Beaten to it by Desslok, but seriously anyone who is thinking minions have no place in a high powered game should try sending 3 groups of 10 of them at their PC's
While I totally agree with you, I can not miss the issue that sending groups of 15 was what out GM did. Planetary scale weapons and light sabers are amazing against those targets. Begs naturally the question why we could use those openly. ;-)
And the most dangerous enemy is the one who controls when, how and who. If players are constantly using heavy weapons than they not only get seen with those weapons everywhere and give enemies time to prepare for those weapons, but they might indeed get easily trapped by simply playing the local authorities against them. Usually you can not just shoot in a city with heavy weaponry and expect your ship waiting untouched at the port for you some hours later.