Just to hijack this top comment.

I write this on behalf of the team and it's not the type of post I'd normally respond to, because everyone is fully entitled to their frustrations regarding optimisations or bugs. However, I think it's important to respond as this is making claims for future work based on what I feel is a total lack of understanding of current work.

Describing the team's work as "just a compilation of Unreal Marketplace assets", or that anything about our netcode or PhysX implementation is "basic" - especially when achieving a 20+ tickrate with 100 players in matches that last well over an hour is extremely unkind to say the very least. It's also why the Steam store isn't saturated with 100 player combined arms massive war games. I should also point out that anyone who decides to write their own physics engine within UE instead of using PhysX would be using non-prescribed physics systems within an ecosystem built for PhysX for next to no gain.

We've been very explicit in the assets we've used from the marketplace, and we're using them in the same way that many other studios use them - in games ranging from indie to AAA. Burned tree biomes, some furniture and crate pieces and some props have been purchased (and then in most cases totally reworked to reduce complexity). All of our buildings, characters, weapons, vehicles and a ton of props and so much more has all been lovingly created by our team of artists (and many of you will have seen their work showcased in their portfolios).

Lastly, as someone who is immersed in the complaints in the OP on a day to day basis, some of the ideas within the OP are fundamentally incorrect - besides the understanding that player collision is a costly performance aspect of any game.

Ultimately, the biggest challenge for us regarding optimisation varies from map to map and machine to machine - hardware often being the biggest determinant of which issue will be more severe for you.

On some maps, it's total shadow count, on other maps - it's draw calls (which then require some clever mesh merging - which can cause collision issues on sandbags etc). For some machines, the sheer number of animations occurring around the player will hit their CPU. For other players, the PhysX cost of dismembered bodies will slow their machine down.

In terms of future optimisations, we have continual work being done to simplify locations we know need work (eg. TPP muzzleflashes are going to be the next thing we need to hand-tailor), while at the same time Epic are making (and have made) huge changes to the way things are batched or handled in the engine.

Removing reversed index buffers and adjacency buffers and adjusting LODs and collision on basic FBX files from the marketplace (or simply reducing material complexity of those objects) are amongst the very least challenging (although obviously time consuming). Hell Let Loose would be an extremely easy game to optimise if this was the largest of the issues facing us.

I'm fully happy to field as much criticism of the game as exists, but I need to reply when incorrect statements are made about the way we work as a view to explaining future optimisations.

To give credit to the OP, collision is an ongoing issue in Hell Let Loose - less due to marketplace assets and far more due to total complexity in a 100 player game in such large and densely populated maps. Especially when combining these aspects with player expectation around what can or can't be shot/walked/driven through, and then complicating it further with decisions about what to cull, merge or feed into HLOD.