I love tanks too, but yes troopers are vital to their success. If you're taking them then you may as well make use of them, troops without upgrade are a missed opportunity! Even just flamers on the Vets would make a significant improvement for a low cost as they could clear enemy infantry away from your armour much more efficiently.
I'm not sure what the Lord Commissar is for, probably better to replace him with some psykers for some buffs - especially if you want to run an entire squadron of Vanquishers! Maybe also a Techpriest to keep them trucking and provide PotMS? I prefer squadrons of 2 tanks, as they're more mobile and let you spread the tanks out a bit more, at 2000pts the Valkyrie will be nice but I'd drop the heavy bolters as they are sadly overpriced for their limited use - much better to get the pods for some capable anti-personnel fire in my opinion. That or replace it with a Vendetta for flyer hunting?
The Sisters will provide a solid core to help protect your armour and seize objectives but again wasted without upgrades! I'd drop the CS as you'd get more from standard units to bulk your numbers up and stick the Canoness in with a squad and give them upgrades, they could do some good for you either attacking or defending. The Vanquisher sponsons are also an option to save points, as you'd want them to be far from the enemy if possible.
The list has a good core and theme to it, but I think it could improve quite a bit (hence the long post!).