What is more important: Snap aggro or being easily to heal and survive well?
Expertise (as hit) only helps you for a few seconds. Survival stats help you through the whole encounter. Sure, if you outgear the content, it's ok to go for hit/expertise but for actual content it should not be relevant. (At least as long as you don't have problems to beat some enrage mechanic or something, but that would be just special encounters and maybe it's a better idea to let your DD think about what they are doing wrong, anyway.)
Sure, with low expertise and hit, you will not always have the snap aggro right from the beginning, because you can miss the first attack. But taunt does not miss anymore. So you have something to get the attention of the mob back. And most of your attacks will connect.
Many people posting here have hit lower then 3% and expertise much lower than 5.
That's speaking as a warrior. We have more or less the same mechanics as paladins, but are dependant much more on getting early hits on our opponent, because we don't start with a full resource bar and 3HP.
If we need to be hit capped (for interrupting) we can just eat hit food or drink a hit elexier.