For the longest time, when I PvP'ed in Cyrodiil I would always play the annoying tank role. I would chain people with both unrelenting grip and swarm mother. I would reflect and absorb projectiles and I would CC and debuff with Talons and Reverberating Bash and Fasalla's. However, when I started doing BG's I noticed I couldn't really do that in the same way. The tank role I was playing was meant for larger groups and was not sustainable in BG's. I didn't contribute enough in damage and the CC's and Debuffs didn't work as well cause everyone was almost always immune anyone, in cyrodiil that was different cause I could always swap targets to someone that was not immune.

Now my recommendation for you is yes, stay tanky, but find a way to deal damage or heal as well that fits your play style. For me that was Knight Slayer, a fully charged heavy attack would deal 9% of a targets HP in unresistable oblivion damage, combine that with an infused weapon enchanted with even more oblivion damage and can actually fight while still being tanky. I looked into these changes cause I was tired of not getting assists even though I helped attack the targets, there is a damage limit you need go past to count for assists and so while I was tanky and didn't die often I wasn't getting any points in anything but Capture the flag really, or if I was lucky enough to be the person on my team to pick up a relic.

But so again, try that and combine that with a heavy armor set or a crafted set on your armor pieces and you can be tanky and still deal damage, I have even managed to kill people in 1v1 and once in 1v2 with that set. I would also recommend back bar'ing either 2h or Dual wield for some extra utility and skills. I did 2h first but gonna try Dual wield, will be trying to get Axes in Infused for my Knight slayer to give out strong bleeds with 2 enchant procs on that, 1 oblivion and 1 disease. Damage and Debuffs.

This style of PvP Tanking is not for everyone but its my experience with it so hopefully you find this helpful. in TL;DR, little bit of damage while staying tanky is the way to go, overly tanky with no damage is not as good.