Tank/herc is a very strong strategy, but it has to be used with the correct expectations. Unless your micro is really good and practiced, it’s going to be hard to repeal large waves, for instance. It’s also ground-only, obviously.
I think it’s helpful to think of the tank/herc as a tactical missile. Move in strategically, drop the tanks at a safe distance, give them a volley or two, then scoop up and reposition. It’s not a brute-force tactic, and if you’re trying to clear something, it takes time. It’s also helpful to have a couple of science vessels on follow. They will keep your herc topped off.
When it comes to big pushes, use the ARES bots. They are extremely tanky, and create a great pocket for the tanks to sit in. Or wait for the ally to attack then use the tank/herc to “snipe.”
Mechanically, make a control group with the tanks. When they drop, immediately select the tanks using the group number. When they’re ready to be picked up (almost immediately in most cases), right click on the herc. There are lots of ways to get fancy with this (that I don’t use cause I also suck at micro) but this is an extremely straight forward way that works.
Tank/herc tends to lack the oomph needed for late game work by themselves, so unless you want to juggle lots of hercs, keep the tanks in their tactical role and then add other units to form the bulk of the army.
Goliath/vessel is probably the standard late game Swann army. Upgraded goliaths are extremely potent against air, and with the tanks wasting ground forces it’s very strong (albiet micro intensive). Mix in Thors if you want more anti-ground or to make the army more durable. Just make sure to use defensive matrix because the Thors are too expensive to lose.
Don’t forget about Wraiths either. They’re too fragile to take an army out of, but they make excellent support units/firefighters.
My suggestions for getting Swann to click though is 1) make sure you hit your early build order. Swann using turrets can expand pretty fast, and he needs a strong econ with lots of upgrades. 2) use the Bots early and often. They can fill a lot of space, especially with mastery upgrades, and carry you on most maps until other units are made.