With stealth armor automatically incorporating an ECM suite, Artemis IV (or V for that matter, or Narc/iNarc) won't help and you'll want to be a bit careful with the C3 as well. After all, it wouldn't do to get your spotter caught in the ECM bubble or even just have it block LOS between them and the rest of the network...so the shortest effective range you're going to get under standard rules (i.e., not using TacOps ECCM) is 7 hexes.
The rest of the tips in this thread I agree with, especially the ones about getting close and messing with the stealth units' heat. ;)
...I don't quite get the point there as the Stealth-equipped unit
itself is treated as being within range of an enemy ECM suite, too...
So, going in with C3 et al against a Stealth-equipped unit is a VERY viable tactic, at least if the rest of your C3 lance/company gives
inferno/plasma surpression fire. ;)
Edit: Actually, the only real advantage I see for Stealth-equipped units is that they cannot be targeted as a secondary target,
requiring concerted effort by you own units and recognition as a priority threat.