I think you will find it depends on how well the armour is supported beneath, what angle to the horizontal the armour is and how much flexibility the armour has been allowed,

For Saint Thor has bent it over the fights it has had. and now and again I have to get the big hammer and do a Quasimodo
ringing session on the drive here at home (the bells they made me deaf you know .)
That is because the axe from Thor hits at an angle on the upper section of the Saint meaning it has point rather than blade contact being close to the top plate there is not much flexibility for the armour so it bends even under the rubber outer skin!! the Saint is made from 3mm ARM steel this is similar to Hardox400.

Cherub is a more standard robot and against Thor the front 3mm ARM did bend Not a lot but enough, the rear section is made from 5mm steel I don't know what the hardness is as the supplier was not sure himself. But it is the same stuff they make the hull of nuclear subs.This did not bend under the Thor hammer and showed only the slightest of dents.

I have found HDPE to be very good as armour, Seraph is made of the stuff, and when NST hit the wheel of Seraph in the UK champs it ejected itself out of the arena but Seraph worked fine. I have 20mm lid on Saint and has proved to be far better than 5mm steel armour and half the weight, the wheels on Saint are 12mm HDPE and they have lasted 2 years now.

Hope that's given you something to think about