Beastmen are really painful to play. Super slow economy, trash T1 and T2 units for the most part. Weak ranged. Bullshit tech tree that costs them money to prevent their research rate from dropping. Can't replenish if you can't go into Hidden (Ambush) Encampment stance. The army lives and dies by upkeep cost reductions or it's not viable, and that requires upgrading your main building in the herd to Level 3, so you can build another building for 15% or so reduction, then to 5 for an upgrade to that building for a 50% upkeep reduction. For reference, Chaos' main building just gives upkeep reduction.
Even in SP it's a rough start. In MP you'll get roflstomped by pretty much any other faction who can spin up faster.
About the only thing it has going for it is Khazark can essentially get "Freestigor" units because he gets massive upkeep and recruitment cost reductions to Beastigors. But that still requires a T5 building, and the upkeep reduction building to be in place.
I just played a campaign with a friend who was running Chaos, and he was literally at max efficiency (doomstacks of Chosen) by turn 50 while I was barely able to field one competent army. The weakness of initial Beastmen units is the first hurdle they have to overcome as a faction, and it comes with just shit loads of unnecessary costs and complications. (Beast moons basically demand that you take a big penalty for a so-so bonus you don't want or need at the time, and it's non-negotiable. +20 growth for no replenishment for example, or instant replenishment for -20 growth.)
If you're not competing with anyone in coop or vs. and want an extra-hardmode hobo start, then play Beastmen. But you'll feel outclassed by every other faction for dozens and dozens and dozens of turns playing them until you get over all the hurdles they put in the way of the faction.
Ironically they were the first faction I played in TW2, because I love Beastmen. So I had no idea how bad they were until I came back a year later and tried out, like, Skaven, who literally shit out money everywhere and their T2 units (Eshin) can carry them almost all the way through the end game.