So I guess I'm going to comment on some of the suggestions:
1. MikeDawg's Mamoswine: HP Fire does indeed give you a good lure, but having the same typing (ground / ground) isn't really something I want to do. With Keldeo, Starmie, Rotom-W, and Rain Teams running a good portion of the metagame, I feel we'd be hard pressed against them. Granted, you could fix this in later building, but that could be said about any of our submissions this early in the submission process. I feel like we should use a partner that can defeat most of Lando's counters, not a certain portion.
I don't see the need to lure out Ferrothorn when setting up on it with Landorus-T is super easy once you pull off an Intimidate. Granted, luring out Skarmory is pretty nice, but I'm sure other Pokemon could do this better. Keep in mind the Mamoswine adds a Rotom-W weakness, Starmie weakness, Keldeo weakness, and rain weakness that Landorus-T already has issues facing.
2. Halcon of Light's Offensive Heatran: Beating Skarmory is nice, but it opens up issues for Starmie and Keldeo. However, the Magma Storm trapper would be a pretty neat idea for a weatherless team that could lure out and kill rain teams early.
I'll comment more on this submission after you edit your OP.
3. Nysyr's Rotom-W: Rotom-W is a pretty good choice: it checks Keldeo, Starmie, Hippo, Skarm, and rain teams in general. The submission itself is pretty solid, if not standard as well.
Keep in mind that Rotom-W and Landorus-T have issues taking down KyuB, as well as having issues facing sun teams. I don't bring these up to bring down the submission; rather, to open eyes so that if we go with Wash other submission will be geared towards fixing these issues.
Also, lastly, Rotom-W and LandoT have problems with LAti@s as well.
4. Trainer Au's SubDiable Gengar: If I was going to submit a Gengar set, I'd use the EB Gengar with Icy wind and Thunder(bolt) to lure out and kill LandoT and Skarm, but in all honesty Gengar isn't a good rain fighter (or Starmie / Rotom-W fighter) and as such I wouldn't vote on him just yet.
5. Hot N Cold's Mixed Jirachi: This is a fantastic submission. By all means, it does everything you said: lures out Landorus-T's counters. The only thing I worry about is LO Analytical Starmie, and Rain Keldeo, but I'm sure this would pair greatly with something like Rotom-W which could sponge all of Starmie's hits and check Keldeo.
6. Jellicent: This by all means isn't bad, as it does beat all of LandoT's counters, but it makes the team geared defensively or balanced and I feel like Landorus-T could thrive on a more offensive route.
7. Signal Beam Rotom-W.
I don't see the point of luring in Celebi when Landorus-T boasts the possible U-turn and will usually force Celebi out, thus earning a free turn of set up.
I'm pretty biased towards Jirachi / Rotom-W submission atm. They are the most solid submissions thus far.