I’m level 11 with Swann, leveling his P3. He has tough time leveling early on, that’s for sure.
You should play to his strength and support your ally. Siege tank + hercules + vessel are definitely his power house, since you get the +40 damage upgrade for tanks right from the start. Upgrade it asap (after around the time you build your first tanks and hercules), next upgrade his laser, so you get his second calldown asap as well. Try to keep one calldown available at any time for emergencies. Warbots are preferable, as they also tank for your tanks
Depending on the map you can often get away with pure tank + hercules + vessel. Occasionally you have to mass goliaths / missile turrets as well, when you are dealing with air.
P1 is weird. Loosing his 2 major calldowns hurts. Though the lasers AoE slow is great when juggling your tanks with hercules around.
P2 is very powerful on defense type maps, even before you get auto repair for structures. You could just level playing temple of the past or dead of night and defend with tanks + turrets. At daytime just take a hercules and support your ally 10+ siege tanks. Probably the easiest maps for Swann.
P3 is very powerful and mobile overall. One full hercules with at least 10 tanks can do a lot.
I never built any cyclones, wraiths or thors while leveling his P1, P2 or P3. Although thors would be nice if you face scourges…
Speaking of… IF you face zerg baneling, scourge, viper, then my main defense was having 5 hercules at all times. I’m not kidding… just suicide 3 empty hercules to absorb any scourges and parasitic bombs. Loosing 2 empty hercules is not a big deal… both cost 200 mins and 100 gas. It is much MUCH preferable to loosing all your vessels.
As cheap as they are, you can also suicide a hercules, to drop a pulse cannon / concentrated beam on an attack wave on the other side of the map. You can also try to time this well, to hit the wave and parts of enemy base defenses with one calldown. And often the hercules even gets out alive, if you don’t teleport exactly on top of a wave.