Cleric is stronger with -50% losses than -40% losses and plague immunity. I understand what you are saying but nesta understands how cleric fits into a kd setup better. The only "good" thing about plague immunity on cleric is hopefully it scares people away from undead and indirectly gives warrior and merchant a massive buff.
Over the past say 15 ages sages rarely had a direct science bonus and when they did it made them stronger than a mystic/rogue at banking and VERY difficult to op. The last time sage was even remotely as strong (i think it was +25% science and 1/4 books/acre) i had my best player run feary sage and by week 8 or 9 he literally could NOT be cast on by a mystic and ran 30% WT+CS to counter rogues. I remember one war the enemy went 1/150 on casting on him, it was just stupid. Compare that to now and +50% ALL science may not directly give a wpa/tpa advantage but it buffs every other part of a prov so massively that you end up with a relatively larger tpa/wpa than we had in the past.