Regardless, if you find yourself in a hopeless battle this is what you should do;
Use your superior speed to run across to around the halfway point of the map and find a nice bush or cluster of bushes to hide behind/hide inside. Sit still and don't attack an enemy that you know you won't be able to hurt, just keep them exposed for your teammates to attack.
If one of your allies deals damage to an enemy tank that they normally could not see, but can because you've spotted them, you will receive HALF of the XP/Credits they earn from damaging that enemy.
If you only see some weak enemies you know you can damage, feel free to engage them. If you see no enemies, rush forward and hunt for the enemy artillery and destroy them.
Tier 4 light tanks are "recon tanks" and thus get paired into high tiers to provide sight for long range fighters/artillery on your team.
Alternatively you can hang around your base and defend it, and protect your allied artillery. You can also follow some heavies around and watch their back.
I would LOVE this to work.. I did buy myself the camo net.. sat in the bushes hand off mouse... BOOM dead... spotted.. couldnt see the tank that shot OR spotted me...