I once asked this type of question of Pete Penseyres. His reply: more base. He was right. Miles per week, zone 2 or above. My guess is that if you rode 200 or so miles per week over the winter, your LT repeat problems would be a lot less. Now, if you are already riding that much, that's another story. Maybe you need to go a little easier out of the box or warm up better before the start. MTB races are notorious for starting fast and thus needing a serious warmup minutes before the start. My .02.

All the training stuff you propose sounds good.