Well, I first recommend that if you're going to just field those units, that you use the Thousand Sons army list from their Index Astartes list, and it gives you access to some very cool stuff (like the free sorcerer).
Thousand Sons are still just as good in close combat as a regular Space Marine, except they can't charge. So what? Sit back and shoot the hell out of your enemies with bolter fire, backed up with amazing psychic weaponry (bolt of change, flames of tzeentch, etc.). It's a shooty army...if you're not comfortable with that, then just play Undivided and field some Thousand Sons -- or play another Chaos power.
Yes, they're a tough army to beat down...but remember that in close combat they can still be cut down, and that heavy weapons will be brought to bear on them.