And yes, galleon is heavily reliant on its teammates, but sometimes you have to fend for yourself in some situations.
In the same respect, your ally should be heavily dependent on you. Sometimes a galleon just needs to ignore whatever is attacking it and focus its fire on whatever target their ally is attacking. Galleons can take enough damage to be able to safely ignore heavy focus and deal out double team damage on one opponent so their ally can return to help. However, in order for this to work, your ally has to fight at an appropriate altitude for you to provide assistance, and you need to have weapons that can provide assistance. This is why hades-lumberjack-heavy flak is a solid left side combo. Even if your balloon has been taken out, you can provide solid support to your ally and get a quick kill so your ally can help you sooner.
The Waddling is currently running double galleons, and I will be the first to admit that it is terrifying to face. They consistently place themselves in positions where focusing, and even getting in the blind spot of, one galleon leaves you completely vulnerable to absurdly fast death from the other. It took me a long time to start learning the power of heavy flak (oh, close to 1000 games...) but when it works, it works beautifully.
But yes, you need a crew who can handle it.
Similarly, you shouldn't take a squid with a newbie crew. There are some decisions that just don't make too much sense. It unfortunately limits what you can do in pub matches, but you can only expect so much out of pub matches.