sounds like the blades have hardened over time and are stuck at one angle if the wiper arms are not bent, this happened on a fairly new set of Bosch normal style wipers i had. Might be something like the washer fluid or prolonged sunlight that has weaken the rubber and then the action of the wiping has set the rubber at an angle causing it to skip.
don't think so, the tips of the blades wash the rain off just fine, but it's the middle section of the blade that gives me problems...
also when there is not enough rain on the screen , it dribbles right over it.
replacing them helps.