Dunno what to make of the new mastery trees :| Very mixed feelings.
For example: Aren't spellvamp and lifesteal defensive options for damage characters (ie, AD/AP carries who would otherwise have no means of keeping themselves alive), so why are they situated in the 3rd tier support masteries? At least when lifesteal was in offensive it made sense. If not in offensive though, why not make them tier one defensive, as they also tend to help keep fighters/tanks going. I've just never seen the need for either effect to be present on a support character seeing as they're not meant to take cs or kills.
Also, being that the new defensive tree has 2 more options over-all (old def tree had 16, new has 18), I feel they should combine the armour/resist masteries in the same way they combined LS and SV. That way, pure defensive players can still utilise the new defensive options whilst not having to sacrifice either armour or resist.
These are just my opinions though, so agree with them or don't, it doesn't really matter. In either case, the new masteries will take some getting used to.