hey there,
you have a great a team so ill give you a rate. The first thing i would say about it is that you lack of stealth rock, which is one of the best move in this game for obvious reasons, so i think you should really try to find a spot. Second, i think some of your choice in the sets are quite questionable. Starting from Tornadus, grass knot seems cool at first to catch gastrodon (which you say is difficult to play around) but i think hp grass is way better for a single reason, it hurts Rotom-w harder. Secondly, i think you should have put U-turn on both tornadus-t and even Landorus to get a well build volturn combo, Substitute on Tornadus-t doesnt really help with everything and its bad because you lose too much hp, Substitute is understable on landorus but still the u-turn would help more to maintain momentum for your team. Also, i would like to point out that noone is suprised by a scarf politoed, its like the most common set, and scarf rotom-w is easily recognizable by the damage output of its moves. Now i agree pretty much with what electrolyte already said, these changes are fine, but i think you can use something else as well.
First, i see you struggle a bit against scizor. truely politoed,starmie and rotom can outspeed and ko, but the problem is that you can actually switch in on it that safely without taking an huge hit, and scizor is always paired with rotom-w so they both puts some pressure on you. I also think that ferrothorn has too much freedom against your team, because starmie, politoed, rotom, even scizor wont do much against it (superpower from scizor kos but you have to watch out for protect) so i would these changes. First, just put Scarf thundurus over rotom-w, because its a way better scarfed if you ask me. It still does the same job, providing a strong volt switch and a nice check for tornadus-t, but its nice speed lets you outspeed problematic things like Ddmence, its typing is better overall since it can come in on scizor taking less damage and threatening rotom-w (it wont like taking thunder)
Also, as someone else said, you have weak somewhat to breloom, and this can fix it thanks to the fight type resist you have now. Thundurus also has access to focus blast which can 2ko ferrothorn making it a less problematic pokemon overall.
Now the other thing i would change here is landorus, for a couple of reason. I know landorus can setup stealth rock by its own, but i dont want to suggest you bulky landorus-t because i think you can go with a more offensive set, which is focus sash terrakion. Terrakion helps you with a few things, tyranitar in general seems a problem and its fighting type provides you a nice switch in for it. Also, sash terrakion is one of the better sr setter to use against sun teams. Just lead against a ninetales and stealth rock as they switch out. Taunt would also help you avoiding deo-d from setting up, starmie can spin for sure but its better to prevent them. Terrakion still hits hard ferrothorn with its stab, and it does a nice job against blissey and chansey, which are problematic otherwhise. Its also very good to counter some threaths under sun like Volcarona, which can be a problem with sun up.