You can easily get uber charge as medic early by having soldiers and demos blew themselves up and buffing others with extra health during setup. If there's enough people to heal and buff you should be able to start with uber charge.
it's still kind of ridiculous though that you have to plan in advance to have soldiers and demos ubered.
like, look at the game mechanics. almost every class has a downside. Heavys can be taken down by Snipers. Snipers are easily distracted, so they don't see behind or to their sides, and also have that dot thing which tells people they are being sniped. Scouts have shit health. Spies decloak on attack. do I need to go on?
the two "fair" classes are the Soldier and Demo. The Demo now is a little harder to use, because his shots don't blow on impact, and he requires positioning and strategy to use well. the Soldier IS the all around class but he doesn't excel in much; decent health and a rocket jump to give him some interesting movement, but rockets are slow, and yeah, all around class.
the Engineer has no such weakness.
NONE.
the weakness that was supposed to be there was resources, but it's so rare to see that affect gameplay anymore. the engineer can heal, via a dispenser. he has a drop with deadly aim and unbelievable range that can be healed and upgraded, and takes a lot of planning to take down. he has a decent shotgun and pistol, about on par with the scouts, and he has decent health. the same weapon he uses for melee is used for healing and for removing sappers, making spies pretty nigh useless since they can just constantly BEAT on shit. and then there are TELEPORTERS which can move the entire team huge distances in a few seconds.
and there's no weakness! every other character can be taken down by one other. an engineer turtled between a dispenser and a turret can't.
it's just ridiculous to me that Valve thought the best update change would be to remove what made the Demoman's first weapon even usable for me and remove Spy reloading, but not lower the engineer's health or slow him down when he's carrying plans or SOMETHING.