Not... really? Thistle still does pretty much the same things as the other two, except for being able to make Fortify Heavy Armor potions instead of the other two Fortify effects, so, like, to make you better at fighting in those suits of metal armor you see in museums. Well it's also part of a Ravage Stamina potion but that's just a way to cause needless suffering that I don't plan on ever making. It's kind of a waste of shards to do both, really.