Re border collies, awwww. :) Your local variety of sheepdog sounds darling. Guide dog criteria can include difficulty of coat maintenance as well, so, say, a keeshond might not be a great guide dog candidate due to all the easily-matted cotton fluff. If I remember correctly, border collies are fluffballs, aren't they? And yes, some breeds have more energy even than a guide dog usually needs.

Re shepherds, ooh. I'm sorry that happened to you. Yikes! They can be fierce, including for the wrong reasons.