Let's see. The only thing I might comment on is adding a steel type to resist ice and dragon type moves. Although Draco Meteor has become less common. It could force you to alter your strategy, but a ton of steel types are slow though, but it's just a soft suggestion. OOoooo What if you use Aggron so the sandstorm improves it's special defense, but then you'd have 2 Pokemon with 4x fighting weakness. Or you could use Hippowdon over T-Tar. But like I said before it's changing your team.
(I would replace Garchomp!)
Item: Choice Band/Rock Gem
Ev's: 4 HP / 252 Atk / 252 SpDef
Metal Burst/Iron Head
(I would replace T-tar!)
Item: Sitrus Berry/Leftovers
Ev's: 252 HP/ 4 Def / 252 SpDef
Crunch/Ice Fang/Thunder Fang
If you still are using Eelektross, I think you should go with Protect > Grass Knot. I mostly use grass moves because my team dislikes the gastro, but fight gem CC, should do very sizable damage to common Gastrodon.
Also, since it still says you are undecided on Protect/Recover for Gastro. I find recover is much more annoying, especially with the defensive spread you have equipped.
I might add I'm a fan of musharna because of discharge and earthquake. Was really useful in vgc for me.
Hopefully you can use some of this! :)