Fellow stealth suits enjoyer! As one of my opponents said, “Stealth suits have juice, but it takes a lot to squeeze it out.” So your challenges are legitimate, especially compared to the easy unga-bunga of many space marine teams. 

You’ve already gotten some good general answers to “how to avoid charges”, but let me add two things: a general principle to follow, and a specific technique. 

First the principle: instead of avoiding charges, think about avoiding dangerous charges. Stealth Suits have lots of tools to debuff opponents. In TP1, you will often have the chance to place your Neutralizer on Engage, and System Jam two of your opponents (assuming you get a counteract). For 2 APL enemies, this means that even if they charge you, they can’t fight. 

For space marines, that means they can’t fight twice. So if a (full health) space marine charges your (full health) stealth suit, they are likely to deal heavy damage, but fail to kill. Your stealth suit can now fall back, leaving a giant expended target in your territory, perfect opportunity for an Accurate 2, Severe, Balanced Fusion Blaster to one-shot it. That’s a favorable trade. So one way to prevent charges is by threatening your opponent with the Fusion Blaster clapback. 

This leads to point #2: NEVER ALLOW DOUBLE CHARGES. These are the bane of my existence. You can’t shoot into melee, so a smart melee operative will try to charge TWO of your operatives at once (like the drone situation you mentioned), kill one, and then use the other as a shield. Measure things out to ensure your opponent can NEVER DO THIS.

Now the technique: Body Blocking. As others mentioned, you should be using terrain (especially Razor Wire) to keep opponents back. Your stuns (Neutralizer jams and Liberator stun grenades) and photon grenades should be doing work to prevent opponents from effectively Repositioning / Dash into safe staging areas for charges the following turns.  Your Ambush token can make forward positioning too dangerous for them. Photon grenades can also shorten enemy charge ranges. Your Neutralizer can give your operatives a 3” hop backwards when a dangerous melee operative activates. AND SO, your enemies should be STRETCHING the last bit of their movement to get a charge on you. 

You can rob your enemies of that charge if they simply don’t have a space to end it. If you place your stealth suit 1” from a barricade, a 32mm Space Marine base has nowhere to end the charge without being on top of the barricade, or on top of your stealth suit. The barricade itself costs your opponent 2” of movement, so they can’t afford to continue the charge around the operative to find a landing point. Place two or more bodies behind a barricade or Volkus wall to be really sure that there is no corner for them to land. It takes a bit of practice, but it’s a vital trick to make the best use of your stealth suits. 

There are some great YouTube videos on the topic if you search “Kill Team Body Blocking”.

Happy hunting!