You do realize where a tank is hit makes a huge difference, right? Also, you forgot the most important detail : Rhinos deploy infantry from it's back door, thus making it much less appropriate for, say, withstanding a rokkit launcha round. Even hitting the back of the armor makes little to no difference.
I BEG YOUR PARDON!? US ORKS DUN KNOW SCIENCE?! I'll have you know our Mekz can make stuff that can blow the crap out of anythin' you bloody hoomies can put up. An I don't see any of you hoomies takin over a MOON an' weaponizin' it into a DEFFMOON! You better get your facts straight, Orkz is betta than all the other factions, cuz we is kunning. Maybe we'z born wif it, but it definitely ain't no lack of knowledge over ere.
I just got my first Rokkit launcha. It came out of a 5k box. It seems to be the "bad" one doing only 600 damage. Feels bad man.
The short/incorrect answer is that tank armor is now designed to explode. How do you stop a force? With an equal and opposing force.
orks do not have specialised antiarmor rockets. They're crude tubes packed with whatever explosive material they can find laying around in a swamp. They have no armor penetrating ability and shouldn't be expected to do much against armored vehicles Orks should be taking down vehicles en masse, by flinging things at it until it buckles under the strain. thats why they all have rokkit pistols
To counter any kind of HEAT rounds you just put additional buffer layer over you armor. What they do is literally take some rubbish, or a fence, and stick it on the tank 30cm away from the hull. Looks kinda orkish.