What helmet are you rocking with on your spearmen? And what is the AP on your crafted Riot Armor? I have 52 with Regen vest. kevlar, burrower shield, and reinforced fabric, which is way higher than I thought it would be.
NVG detection goggles, always. I go for versatility and mobility with this guy: riot gear with TiChrome riot shield, pig boots with high-density padding and spring, total armor penalty currently 41%, 42 MP. Once I get near to level 30, I'll have 3 more Agility and Strider, so I'll have 54+ MP; might be able to hit 60.
Speaking of spear guys, the way to wreck Death Stalkers (and every other stealth melee guy) late game is Fend. You see, you can keep Fend up 99.9% of the time while walking around in real time, the only small delay being the time it takes to spam the hotkey.
Flares? Molotovs? Detect them before they can detect you? Nah dawg, literally stand in one spot and press Fend until they appear, uselessly whip their gay shitty little stinger against your invincible spear, then perforate them and rip out their glands to poison your throwing knives with.