How many draw calls should I target for PC

I've been able to lower the triangles count in the frustum by optimizing grasses and trees meshes.
The tris count dropped by at least 45%.

 

Tweak some of the terrain performance settings, usually terrains eat up a lot.. After that I'd leave it, seems fine to me..

 

@ShadowK Thank you for the advices!
I hesitate to get rid of builtin terrain for terrain meshes, but I don't now if it's worth the effort...

 

Nah the default Unity terrain is fine, you just need to mess around with the settings to get it to run better..

http://docs.unity3d.com/Manual/terrain-OtherSettings.html

The three things which help the most: Pixel error, basemap distortion and BE CAREFUL WITH the next one.

Detail resolution, I usually set it to 512 out the box. If you change it, it will DELETE all your grass etc.

 

@ShadowK you made my day!
I've combined voltage lines and roads to reclaim a few batches.
Then I've raised the pixel error to 10 and set the Base Map Distance to 250:

 

Just to finish off, don't forget to re-bake UMBRA.. http://docs.unity3d.com/Manual/OcclusionCulling.html

Decent occlusion culling will help no end, tweak the settings and make sure you don't end up with meshes disappearing. After that, you could use baked lighting which will also help dramatically improve performance.. Although dependant on how large your scene is, it might not be a good idea..

After that I'd say you're done.. What GPU are you using out of curiosity?

 

Yeah I use Umbra and already have refined the settings.

My GPU is a MSI GTX760 Twin Frozr OC.

 

I ended up tweaking things a bit more.
I've lowered pixel error to 8 and raised up base map distance to 300 for the terrain and I've disabled the shadow cascades: it gives much smoother shadows which is perfect for that kind of dark atmosphere.
As a result it decreased batches, triangles count and shadow casters.