As for your ridiculous assertion that Clerics shouldn't have powers comparable to Knights, you shouldn't be talking about balance then if you support the ridiculous notion that one character has to be indisputably better than the other. Either nerf knights or buff clerics until their power becomes more even, else we can't talk about balanced environment and nothing will change in the end.
Thats the whole point of balancing? Giving every class strengths in which they are untouched by others or else why even play more than 1 class?
As far as the website goes, OS seems to be having a different interpretation because on the german website it says "Cleric are in the back lines supporting their allies" "They can be combat clerics if you skill them that way" "guardian has better healing and the holy knight has the better boosting abilitys". So there goes your argument.