Talk:VPBE/@comment-24795478-20150530133415/@comment-24241876-20150530140108

Maokai and Singed may probably get it soon, especially because of how old these champions are, but the reason they didn't get it during their small reworks/updates was because they were already strong, and didn't need MR/Level to make their tankiness even better. They haven't received too many changes since. (The influx of Maokai Top, being very tanky already with his ultimate, or Singed Pre-S3, when his ultimate still gave tenacity, although that was a long time ago, and he still doesn't have MR/Level.)

Poppy will probably get MR/Level when she gets her rework. Especially if/when they give her a new passive instead of the current one, that makes her increasingly harder to kill as she is closer to dying.

Kassadin doesn't need MR/Level because his passive already reduces magic damage, and his build and kit capitalize on that advantage. (Seraph + RoA, Q Shield) Simply put, Riot didn't want Kassadin having %DMG reduction and growing resistances because that would render him nearly impossible to kill by magic damage later in the game (and it doesn't sound fun being unable to kill an assassin because they're too tanky), so they removed it.

It was stated that Yasuo did not get MR/Level on release because he was intended for midlane, and that his shield (which had a much higher value at the time) already made it hard for mages to deal with him, so they kept his bases at 30 the whole game. (Coincidentally, CertainlyT, the designer for Yasuo, stated that in retrospect, it probably would have been better to give Yasuo lower base MR, at about 25 or so, while still giving him MR/Level.)