Went to my weekly MMA class 3 days ago, and the session focused on boxing. Everyone was assigned a partner at the end to spar with, and out of no where, my instructor shouted everyone stop! He then got us all to observe these two heavyweights who were sparring and he said watch these two and tell me what you see is wrong. These two heavyweights then went into sparring mode and my impression was that they were slow, predictable and solely focusing on power. My coach then told them to stop and said "What you see in front of you is a shabby display of boxing which only demonstrates power and how to gas within 2 minutes". He then brought up Overeem as an example how he has average boxing at best and how he needs to get rid of Roberto Flamingo as his striking coach if he wants to improve on his striking.
I have always been critical of overeem, and this little lecture from my coach really reinforced the fact that overeems striking is not as good as people make it out to be and his boxing definitely is far from elite. Ive rarely seen overeem throw any combos at all, his boxing defence is crap (always relied on those big K1 cushions to block shots, doesnt work in MMA for him) and his boxing power is also disappointing for how big he is, and I put that down to his technique.
Overeem has relied to much on his knees throughout his career, and it was effective against lower calibre fighters, however in the UFC, ones boxing ive found has to be solid and effective otherwise you will have a disadvantage on the feet.
I think if Frank Mir can surive the first few mins against overeem, then I think Frank can outbox him and score the Knockout. But personally I think that match is a made fight for overeem who will use his clinch and press Mir up against the cage to then score the KO.