I find that there are three types of tanks.

1. Insecure tanks learning their role who often pull smaller groups because they aren't confident in either themselves or the party with larger ones. Whether these are sprouts or just cautious players be considerate and help them discover their limits (and your own if you're a healer).

2. Confident tanks who know their capabilities and actively utilize tank stance and cooldowns as needed to pull massive groups of mobs and mitigate them to the best of their ability. These are the good players, and try to do your best to keep up with them. If they're maximizing their toolkit then try to do your best to maximize yours, and suddenly the dungeon becomes if no more fun more interesting for the both of you (and maybe a little less tedious for all).

3. Bad tanks who act like confident tanks but either forget they have mitigation cooldowns or don't know how best to use them. This includes tanks that lose aggro multiple times, tanks that gather large groups and end up at 20% HP before they even stop moving and then fail to pop Hallowed/LD/Holmgang, and those that try to do the same in the DPS stance without overcompensating either with AoE enmity skills to hold aggro or defense cooldowns during critical moments.

You will see some of all three of these. Be considerate to #1 and try to build their confidence with friendly banter, get along and try your best with #2, and treat #3 depending on how they treat the rest of you. If they're still learning then it's good to be supportive but if they're just nasty-bad then don't waste your time.