I have played a lot of Sons games the past few months with the following lists:
Siege1 - Centurion - Centurion - Squire Strangewayes GMCA x2 Falk Ragman Gun Mages w/ UA - Cyclone Black 13 Aiyana and Holt /Murdoch
Centurions and Covering Fire help keep from getting jammed and the Centurians can hold zones, but being flimsy and ranged with the rest of the army means I don’t contest flags well. Expensive solos and A&H mean the army is thin. Basically most my games have great turn two Feats that eats a large chunk of the enemy army and then I lose on scenario or lose Siege because I moved up to far getting people in Feat. Once I did live the dream and hit Conquest with Kiss, Rune Marked, and Death Field and gunned him down. Got a Dracodile with Rune Mark and Ragman with an Arcane Reinforced Centurion, but then Barnabas2 ghosted through a house and ate Siege.
Haley1 - Defender - Defender - Squire Jr. - Sentinel GMCA x2 Riflemen x2 Falk Gun Mages w/ UA - Cyclone Black 13 Strangewayes
This list has performed pretty well, but still feels thin an doesn’t contest well. Really holding ground is the main weakness of this theme. Both lists attrition well and threat ranged assassination but they don’t really bully the table in any way. I have some changes in mind but don’t have the models I want yet.
My biggest problem with Cygnar in general right now is SR 2018. I feel like Storm Division is just a little off from being great and Sons has insane damage output potential, but both themes fall apart on scenario pretty fast, especially Mirage, Spread the net, and Recon 2, but even the others can be a problem. Your only option is to totally remove all of their solos (which is why the solos in Sons are so amazing) and hope that you can contest zones reliably enough. The far zone in Spread the Net is a massive problem for these kinds of lists, to the point where it feels like you can't drop them at all unless you're confident you can get a Centuion back there and keep him alive (not a safe bet into most of the meta right now).
I'm not really sure how to build lists that fix this in either theme. Trencher lists are so much stronger at getting to zones and keeping contesting elements alive while still having great tools to snipe out solos. I'm not sure how Sons can make that happen without having to reliably murder half a list in a turn, which means that Siege1 and Haley1 are the tools you want to bring, but after the feat is over, if you haven't killed enough, you just lose. Terrain is a major factor here, even with mage sight.
Wrll i have found that cygnar has an amazing cheap scoring unit. The non-trencher machanics. The gobber grunts are amazing at def 14 and add in the unit is 4 guys for 3 points it is an easy to use contest and scoring piece. It is the main reason i have used one unit in my sons list, but my list runs 4 jacks so repairs are good.
Game 1 my opponent won the roll and chose to go second.
Turn 1, running forward i used two hills to place my Haley 1, squire, and black 13th on two hills trying to protect them from my opponents attacks.
Haley arcs arcane sheild to black 13th
Opponent turn 1. He placing Dauntless Resolve onto Stormlances, places Snipe on Stormstrider, Assail on the Iornclad. Then walked forward.
Lances and jacks run foward. Stormstrider advances and fires 2 boosted shots into my gobber tinker, both miss needing 12's to hit.
Cain places fire for effect on ace. And advances.
Ace walks forward and shoots at ryan 1 of my black 13th. Using magic bullet ace hits but rolls 3 on boosted damage. The magic bullet crushes 12 on the die Lynch dies.
My turn 2. I feated with haley 1 placing out Temporal Barrier and Deadeye on my Arcane Tempest Gun Mages..
Using my hunter, remaining two black 13th, and haley 1 i managed to destroy ace, two stormlances and leaving the last knocked down on 1hp.
Arcane gun mages place a few points of damage into the stormstrider.
Opponents turn 2 Opponent uses caine 0 to kill my remaining black 13th. The storm strider takes out 5 of my gun mages. He also places his firefly into the zone.
My turn 3. I take out the firefly, and place my full battlegroup into the zone. Using the hunter i placed 5 damage onto his Iornclad.
My remaining two Gun Mages charge the deal 3 damage to the stormstrider total. I use haley to kill the last stormlance and cast Temporal Barrier.
Last gunmage captain kills caine 0.
I score scenerio 1-0
My opponents turn 3 (grind turn) Opponent feats and wipes out my firefly, lancer, iornclad, a gun mage captain .
Opponent scores 1-1
My turn 4
Back to wall i try to assassinate beth 1 and leave her on 1 hp.
My opponents turn 4. He kills me with a charging savio.
The game was fun we both enjoyed it and after talking we decided. The gun mages are usable and can deal good damage to my opponents high armor. At def 14 most my models are doggy enough vs non boosted attacks.
Going i to the game not intending to win i am glad that the army can handle armor and is flexible enough to keep scemrrio alive.
(I will post next to games later once i reread my notes)
Cygnar Army - 75 / 75 points [Theme] Storm Division
[Haley 2] Major Victoria Haley [+25] - Centurion  - Stormclad  - Thorn  - Squire [0(5)] Anastasia di Bray  Journeyman Warcaster [0(4)] - Charger  Major Katherine Laddermore  Storm Lances (min)  Storm Lances (max) 
The Siege1 list I played 5 times, going 4-1 (losing once to Lich3 Slayers). It can be bothered by some scenarios, such as Mirage, but I did bring Haley2 who loves mirage to complement Siege1. I would've brought Haley3 and Siege1 if I was the only cygnar player in my team though.
The list is very strong, does tons of work, actually withstands jamming VERY well. Siege1 in Sons with a limited BG is also pretty "idiot-proof" since he hasn't got a lot to do with his focus except sit in a Foxhole with a SG and camp (and blowing stuff up!).
I wish I could choose one MVP from the list - Caine0 comes to mind, essentially making Siege1 viable himself. But Alexia1 does so much for the list with scaring away jammers, scoring flags (with the thralls), contesting far zones (with thralls) long enough to win the attrition war. But then again, the B13 hit like actual trucks and the ATGM really make the list sing with the sheer number of thunderbolts they bring. The weakest part of the list is easily the Blazers.