I love this game, very enjoyable and I feel like when I get killed its not in an unfair manner unlike certain other games *cough* black ops *cough*

The only issue I have with the game is that people are able to see me at a distance despite me having cloak on.

There's a perk for more easily spoting cloked enemies = Cloak Tracker. They might be using it.

That is a possibility.
They could also be using Visor Enhance as well.

Well all i can say is PLAY more, it just takes getting use to the game. Once you get use to toggling armor and invisibility, add perks that match your gamestyle, and have a great map knowledge. Youll pawn.

Yeh i needed time also to get used to it.
On my demo account (US) my kd was like 1.5 or something in that direction.
And i got better from time to time.
On my EU acc my kd is 2.93 now ;D
btw: try using different weapons to get more flexible if you have to pick up weapons ( happens often with the feline)