Drop Troops

so I was bouncing Ideas around and had a thought, I dont belive they can but could a techpriest acting as a indpendent character join a squad and use the drop troop rule?

No not in 4th. He doesnt have the deep strike special rule or access to buying. Plus the way reserves work is you would have to role seperatley for them and then if they both come in you could deep strike. That kills the whole idea of joining IC's to squads like that.

thats not always true or people play it wrong since you could drop pod IC's with marine squads(have seen it done) or things like deathcompany and their chaplin

Your missing the point though. Unless they have it state specifically for them they can't. They should not be doing that. As steve stated earlier you have to roll for them seperately unless it is a retinue. In which case if someone is doing that then you've been gettin cheated lol.

the death company isnt but I have seen/heard of them dropping with the chaplin that was my point

If your death co and chappy both have jump packs and you make two seperate reserver roles you can deepstrike them together. Just like regular marine hq's and 8 man or less drop pod squads. IF both become available in the same turn then yea you can do it. But a regular HQ on foot doesnt have deep strike as a special rule.

steve that makes no since yea the leader is going to jump into a droppod and join a dropping unit, yea makes a whole ton of since there

Doesnt have to make since, its how 40k in 4th edition works bruce.