they were had paid for be so powerful, they paid with a hard time leveling up, hard time getting cash and rune making was not very possible because it take about 10 hours to make 3 bp sds.
Knights was not supposed to make damage, but however they could block nearly anything thanks to their healing runes, but in return of no attack, they got the block, and also they are cheap and get easy cash.
you get my point?
Tibia today is balanced in a fucked up way, balanced doesn't mean they attack with same damage!