I have considered all of the above points mentioned and here is how I plan to deal with them-
Note: My plan with Xatu is to use it as a substitute for Bronzong, with the added benefit of denying free rocks at the very start of the game.
Scizor- Xatu is not supposed to switch INTO Scizor, rather stay IN on Scizor hence HeatWave. (Gastrodon can take a few stray hits from Scizor if need be)
Breloom- I do struggle with breloom, especially if it decides to predict my Xatu switch, However 57% Brelooms runs Sash so OHKO wouldnt mean anything without rocks, and with rocks I with ensure that breloom cant come in again. (Tho it will be a problem if it predicts)
Garchomp- I believe there was a slight mis calc on your part (Maybe lvl 50 and/or 130 bp draco/-2 spa)
252 SpA Life Orb Garchomp Draco Meteor over 2 turns vs. 252 HP / 192+ SpD Xatu: 153-183 (88.9 - 106.3%) -- 31.3% chance to 2HKO after Leftovers recovery.
I plan to set up Trick Room turn 1 and teleport/hard switching on turn 2 essentially playing the role of a TR bronzong while denying rocks.
Jellicent is a good mon for this team, true, but the utility provided by gastrodon seems more valuable to me. Shutting down rain and rotom, while also setting up rocks is very important imo.
However if you can suggest a different defensive core to run along with Jellicent I am all ears. (Like Jellicent + X mon instead of Xatu)
Also also thanks for ur feedback