Tandoori chicken and kebabs are threaded onto skewers and let down into the oven for rapid cooking in the high heat. Chicken quarters can take as little as 10 minutes to cook. I've read that restaurants use an onion gravy which, I imagine, is similar to your basic curry sauce. I can't believe that a restaurant would use an enormous blender for the sauce. Yes you're right.
All restaurants use a stock sauce.
And, yes, they DO use a blender but not the familiar kitchen type. A curry chef would use a huge hand held blender with a rotating blade on the end. You can buy smaller versions for home use but they are about a foot long and pretty weedy. The industrial version is about 3 feet long and quite heavy. In a restaurant they boil down the onions with garlic, ginger and spices and puree it all right there in the pan.