These are the big boys in Invading Clans
304TH ASSAULT CLUSTER
THE HOWLING BEARS
Star Colonel Paul Vishio
Supernova Trinary Command (Star Captain Dillan Vong)
Alpha, Bravo and Charlie Command Stars (5 OmniMechs, 5 Elemental Points each)
321 st Assault Trinary (Star Captain Vegara Ortiz)
Alpha, Bravo and Charlie Assault Stars (5 OmniMechs each)
14th Assault Supernova (Star Captain Bernard Bazso)
Alpha, Bravo and Charlie Assault Stars (5 OmniMechs, 5 Elemental Points each)
72nd Assault Tri nary (Star Captain Edwin Bekker)
Alpha, Bravo and Charlie Assault Stars (5 OmniMechs each)
1st Elemental Support Binary (Star Captain Ossin Vong)
Alpha and Bravo Elemental Stars (5 Elemental Points each)
332ND ASSAULT CLUSTER
THE IOWA BLACKLANCERS
Star Colonel Seija Harlow
Trinary Command (Star Captain Gosvoda Nuyriev)
Alpha, Bravo and Charlie Command Stars (5 OmniMechs each) Tango Fighter Support Star (10 Fighters)
469th Assault Trinary (Star Captain Pinter Hall)
Alpha and Bravo Assault Stars (5 OmniMechs each) Charlie Elemental Star (5 Elemental Points)
2133rd Striker Trinary (Star Captain Jillian Snuka)
Alpha, Bravo and.Charlie Striker Stars (5 OmniMechs each)
23rd Elemental Support Binary (Star Captain Alan Kabrinski)
Alpha and Bravo Elemental Stars (5 Elemental Points each)
Delta Fighter Trinary (Star Captain Lucien Bourjon)
Alpha, Bravo and Charlie Fighter Stars (1 0 Fighters each)
8TH BEAR CUIRASSIERS
THE BLINDING DRIVE
Star Colonel Dana Vishio
Trinary Command (Star Captain Trudy Devon)
Alpha, Bravo and Charlie Command Stars (10 Fighters each)
286th Assault Tri nary (Star Captain Dimon Bekker)
Alpha, Bravo and Charlie Assault Stars (5 OmniMechs each)
90th Striker Trinary (Star Captain Della Ortiz)
Alpha, Bravo and Charlie Striker Stars (5 OmniMechs each)
56th Elemental Support Trinary (Star Captain Tamm Hakimi)
Alpha, Bravo Charlie Elemental Stars (5 Elemental Points each)
47th Fighter Binary (Star Captain Endo Kabrinski)
Alpha and Bravo Fighter Stars (10 Fighters each)
To summarize,
304TH ASSAULT CLUSTER
So 9 Assault Stars, 3 Command Stars, and 8 Elemental Stars
332ND ASSAULT CLUSTER
2 Assault Stars, 3 Command Stars, 3 Striker Stars, 3 Elemental Stars, 4 ASF Stars
8TH BEAR CUIRASSIERS
3 Assault Stars, 3 Striker Stars, 3 Elemental Stars, 5 ASF Stars
I am going to assume the Command Stars are Battle Stars.
So Assault Clusters aren't that heavy. They just have a few Assault Stars ('Mech, ASF etc) to provide bite.
The 357th could be anything. It started the Vega campaign under strength due to the antebellum and may have been relying on tanks for firepower. I don't have the novel to know. They were certainly using Constables rather than Elementals. I suspect until 3145 they would have been happy with what they could get.
After then? Well there is a strong element of players here who consider Omega to be traitors with good reason. The 357th may well be facing a case of getting what they are given and having to like it.