This is my line up:
EOS 70D (2), Lenses: Samyang Fisheye, canons 50mm1.8, 10-22mm, 18-55mm, 70-300L
What do I do:
-wildlife including birds, landscapes, sunsets, waterfalls and so on video. Max outpu: 1920x1080p 25
-time lapses of waterfalls, sunrises, landscapes and more. Max output: 4K-5K
Do I need to improve some area with, lets say, Sigma or Tamron 17-50 or 70 or canon 15-85?
I use non L lens closed to F5.6 minimum.
It seems that there is some consensus around using Canon wide zooms for videography. The 15-35mm L and 17-40mm L are both popular. Though they are going to get pricey if you opt for the IS version, which most folks will want to do, as it helps eliminate camera shake.
Cheaper options would be the non-L series Ultrasonic lenses. Quite a few models come in IS versions. Such as the 35MM.
If you are shooting wildlife you almost certainly want IS, and likely a longer lens, which is money on top of money.