Ok, so we tried a few matches using our guidelines as stated above.
First game was Orks (Beastboss + 10 BeastSnaggas, 10 regular Boys, 3 Squighog Rider, 3 Deffkoptas) vs. Tyranids (40x Meleegaunts, 10x Ranged Gaunts, +warrirors +warrior hero [cant remember, but it was something like this). No one knew which army or list the other one was bringing.
In this game Orks started with a Waaagh T1 > Meleegaunts ran into melee T1, slaughtered Boys, did nothing to the Squighogs > T1 Orks kill almost all of the gaunts > T2 the game is basically over.
We tried a second game, we tried some more extreme lists. Tyranid brought something like: Haruspex, Tyrannofex, cheap warrior hero, min gaunts squad. I used the regular dark angels combat patrol. We played 2 full turns, ended the game after that, because
DA didnt have much left and killed literally nothing (gaunts + hero were camping without
LOS).
Our little experiment ended there.
Basically, if you wanna play combat patrol, use combat patrols