Rashid is the frontline spinner, hes the best one thats there so I picked him. Yardy is worth his place as a batsman, his bowling is a little bonus. Dalrymple is a genuine 2nd spinner who can bat at 7. As far as Yardy goes, he only took 2 championship wickets so hes not going to walk in as a frontline slow bowler. Dalrymple would be more effective because he is a better bowler, I can bowl legbreaks but I dont get to bowl them in front of proper offspinners just because I turn it away from the bat. Aside from that, half the batsmen going around now are lefties so Dalrymple will be moving the ball away from them. As for England never succeeding with 2 spinners, may I suggest this is because they never had 2 good enough at the same time. Broad is probably the primary strike bowler in the side, and for my money is going to be a very good test player. He has all the attributes you highlight in Mahmood, but outbowled him comprehensively when they played together and has done a lot more for Leics than Mahmood has for Lancs.