Is your lactation person an IBCLC? That description of how to use the shield sounds inaccurate. If baby is basing tissue damage, then its not in properly. Did she tell you to turn it inside out (it'll look like a sombrero), place it on the nipple, and then turn it right side out once its on the nipple? It should you more closely that way.
And the milk should not be pooling in the tip of it, if that means there is a lot of empty space in the tip - that will encourage a very shallow latch, which is what causes the tissue damage.
I'd strongly encourage double checking with your LC, and if they're giving you this bad advice (and its not that you've misunderstood) I would get a different one. :-). Many "lactation consultants" are under-trained. The IBCLC credential is the gold standard, and much more training and experience is required before they are allowed tow IRL with the public.