The blockexplorer says Clever finds blocks in a few seconds. The truth is that they might find blocks much faster (about 12 blocks within a second?). That's faster then the blockexplorer can proces. I saw around 12 blocks with age -1Y at the same moment. Why is the algo allow that?

The difference in power between dedicated miners and Clever is way out of control. Boosting the dedicated miners I see as only solution. If we manage to mine the hard blocks quicker then the diff will not fall that much.