DT Swiss rims area freaking nightmare. Never use contis with them. You need to carry three levers for trailside repairs.
Advice, squeeze bead to middle all round, pull the tyre down on both sides towards the ground. Use three levers. One in and hooked onto a spoke, then put the second one in and hook around a spoke. Then put the third one in right next to the second and bend round to hook spoke. The second lever should then be loose. Take it out and put along from the third in the same way. If you keep working them around like this you'll get there. Washing up liquid if necessary.
I've broken park tools levers on DT rims, though, they are absolute bastards to get tyres on and off!