Well, i just made some research in the Shattered Fortress book (and a little in FM:3145 and TRO:3150) and did a recount of the FWL (Tamarind)-MoC/Marian Hegemony war. From that, i made a preliminary butcher's list for the Marian Hegemony. Feel free to help in any thing i might be overlook. Also, in my personal opinion, i presumed that the loosing units retreat unless it is explicitly said that they are destroyed.
I Legio
Tertia Cohors - Destroyed in Illyria (November 3150)
II Legio
Prima Cohors - Damaged after retreating from Hazeldan (August 3150)
Secunda Cohors - Destroyed in Landfall (August 3150)
Tertia Cohors -
Quarta Cohors -
Quinta Cohors -
(I presume that at least two of this Cohors were in Illyria (November 3150), and the other reinforced it when Prefect Kilgore reinforced the planet (early December 3150)
II Secunda Auxilia Legio - Destroyed in Landfall (August 3150)
II Caelum Wing - Destroyed or damaged in Illyria (November 3150)
III Legio
Elements are destroyed in Huntington after their dropships are destroyed (August 3150)
IV Legio
I presume that the IV Legio´s Mech Cohors took some damage in their raids to Campoleone and Astrokaszy.
IV's Prima and Secunda Auxilia Legio took some damage in Ballalaba and retreated (to Horatious and/or Pompey? or Baccalieu?)
V Legio
Totally destroyed by Camacho's Caballeros in 3147. The number "5" is apparently cursed, isn't?
VI Legio
Again, after facing the Canopian counter attack in Marantha, Gambillion and the other canopian planets, i can see the mech cohors whit some damage.
VI Prima Auxilia Legio - Destroyed (October 3150)
VI Caelum Wing - Retreated? They downed a Markson´s Marauder dropship, but i presume they retreated after the Auxilia Legio was destroyed (October 3150)
Dragonslayers
This guys were a regiment at 55% in 3145, and they retreat after some combat from Saint Nicolas in August 3150. They retreated deeper into the Hegemony, or the Gibraltar island?
The Head Hunters
Now i think its the final nail in the Head Hunter coffin. They were a battalion at 80% in 3145, and the Camacho's Caballeros capture 2 companies in a nightime drop in early September 3150. Now, captured can be "you and you equipment are seized during the conflict" or "welcome to the dispossessed ranks". Ether way, they are, at best, at 1 company strengh.
In resume: We are seeing one destroyed Legio (the V), and two heavily damaged ones (II and III), plus a merc battalion out of combat. It could be worse to be sincere. Now, the thing is that the enemy in both fronts will have some logistical issues.
The canopians are way far from their friendly lines, so i can see them pillaging both Ballalaba and Islington, and retreating.
Now the Marik are trickier. The Fontaine´s taskforce is said to be composed of "regiments of mercenaries" and the 1st, 7th and 8th Tamarind Regulars, plus the Camacho's Caballeros, and we know that at least all or significant parts of that units are in Illyria to the end of 3150. We also know that elements of the III Legio clashed (and damaged) with elements of the 7th Tamarind Regulars in Tormentine in (probably) September 3150 (TRO 3150 Testudo entry). So, while they conquered all the planets connecting Illyria with the FWL, i presume that those planets are garrisoned with parts of those "regiments of mercenaries". It would be a shame that those planets suffered attacks from, shall we say, the I or IV Legios? The thing is, Illyria have to be a hot coal to hold, as Fontaine planned for a quick operation. And add the political pressure that Fontaine is getting from the FWL Parliament, with the internal tariff hurting the duchy's economy, plus the political fallout inside the neo-FWL.