To use the Relentless Rats again, if the Rats prove popular but not troublesome, it increases the chances of R&D breaking the four card limit rule again
Five lands drains each of your opponents for 10 life in that situation, not to mention the card draw
If they were suddenly to print a card that was functionally the same or very similar to it, but it only cost 3 mana, then I doubt it would hold that price, despite limited supply
Performance of Sword
While Chazz went around and defeated Duel Academy students to make them Society of Light members, Sartorius wondered how Jaden won and he later found out through his cards that Jaden was the one he should go after to further his plans, not Aster(In the dub, it was also because Aster was of no use to him)
(2) is the familiar escape effect, but there is an additional effect here