Depends on your macro I guess - but between Eng Bay and outlaw upgrades I always spend resources as fast as I can get them, so Outlaw Availability is a total waste - by the time I have a spare 1000M/200G the next outlaw is always ready. Same goes for Medivac Cooldown - once you have the ability to make 3, there is pretty much one always available. Just make sure to walk not fly in the down time periods between attack waves. The only Mastery I am iffy about is the first one, i usually split that to boost Tychus attack speed, and cooldown grenade by a little.
As people have said the best way to deal with Air composition (terran or protoss) is to use Vega and Sykes in some order. Just throw the turrets down between you and the attack wave to slow them down and then steal a few BCs/Void Rays/Carriers. For Air Zerg, Nyx is better to shred them with his storm.
FYI - I play Tychus as my main and always use TYCHUS - RATTLESNAKE - VEGA - SYKES - NYX. The only exception is Dead of Night and Farmer Evac in which I replace SYKES with BLAZE. You can replace Rattlesnake with Niadra if you MUST but under no circumstances should you use both.
Edit #2 - leaving out Sneaky Sam even on Oblivion Express isn’t really an issue, between Tychus, Rattesnake, Sykes, and mind controlled Heavy Units (such as Aberrations, Thors, etc) your damage output should be high enough to deal with the Trains just fine, unless your partner is completely incompetent.