what's wrong with the approach? trainer is with working with us and haven't advised us differently. what do you recommend or see that is wrong?
The use of an E collar in the manner that you described. Working on off lead training before on leash training is extremely reliable. Your mention of cranking the Dogtra up to 70 to get a response when the dog is in drive. Those are the things that I disagree with.
I would work on focus, and engagement. I would teach the recall in a way that is fun and lays a foundation for a super fast and reliable recall. I would teach the dog to heal well on leash, not be reactive to other animals or distractions. I would teach a reliable sit / stay and down stay. Then, and only then would I begin off lead training. Once the dog is taught, trained and proofed with a long line and is better than 85% reliable I would consider an Collar for you and your dog.
If you have a trainer that agrees with your approach and wants to start out by cranking up the E collar, do some more research and find a more qualified trainer. The whole approach that you mentioned is taking to many shortcuts to be reliable down the road. It only takes a few months to gain excellent reliable OB on a dog. I just trained a GSD in 11 sessions to do everything that you want your dog to do. The dog is also super happy, super motivated and never wants to leave his handlers side. The dog was dog aggressive and leash reactive when we started. The dog now walks happily on a leash, recalls are super fast even with other dogs present, and no longer reacts or barks at other dogs. This was done primarily motivationally, no E collar and in 3 months. The dog is now 14 months old. There was no need to wait until the dog was 3 years old to expect it to behave, heel or recall reliably. The main the dog has in it's favor is an owner that works with his dog every day and does it in a manner that lays a good foundation and each session builds on the last.
I'm sure the owner of the dog would give me a lot of credit, he already has. But, the fact of the matter is that all I did was show him how to work with his dog, praise his dog, pay his dog for the right behaviors and guide him. Many folks (like you) are hung up on the tools and the corrections and miss out on the power of praise, reward and payment. That does more to train a dog than a Dogtra at 70.
Please don't take my posts personally, I am not trying to offend you. I can only respond to what you posted as I do not know you or your dog. I do know a little about dog training and E collars, though. Planning on getting an E collar and going to 70 is really a bad plan. You also need to properly condition your dog to the E collar for the training to be effective. Just going higher is a really bad idea and really poor training, IMHO.