Sounds like a 1:1 question being that it's Falken. In which case, Falken tires are made specifically for drift. I'm assuming that this the first time you've used actual drift spec tires. If so, I would recommend that you take them off and swtich back to regular tires until you gain better car control. Once you're in control of your car, the Falken d series tires will only help. It will make it easier to break traction and allow a longer drift with more angle (assuming you do the same thing you did on regular tires).
However, slipping "too hard" may not be a tire issue. Your suspension may not be dialed in. Also, do you have an LSD installed. How are you initiating your drift? It could just be in the technique.
To be honest, with "slipping too hard", there's a TON of things it could be. However, if you weren't having this problem before the tires went on, and nothing else has changed, I'd assume it to be driver error. In which case, you just need to get used to how the car feels with drift spec tires on it. Another thing, Falken drift tires aren't made for dd use. so, if you're driving them to work, school, store, etc...I wouldn't. That's not their intended purpose and you can be at risk.