There should have been a tree dedicated to Tenacity

Some champions are utterly destroyed by CC or by being kited (especially juggernauts, but they're far from being the only ones affected). It would have been a good idea to give them a little helping hand and give them a choice to pick runes that would help them. It would have been a fair choice to give them in exchange for tank or dps stats.

Instead of forcing some champions to take either damage runes or defensive runes, they could pick runes that helped their mobility. Here are a few examples of what such runes could have been:

Merely a setback: After sufferring a slowing debuff, gain movement speed equal to half the slowing effect, for the same duration (max 2 seconds) ex: If Frozen Mallet slows you by 40% for 1.5 seconds, you'd become hasted by 20% for 1.5 seconds once the icy debuff wore off.

Eye for an eye: After suffering any form of crowd control, your next attack against the original caster applies the same crowd control, but for only 0.1 second.

Unstoppable: Suffering any hard CC grants you 10% tenacity for 6 seconds, stacking up to 10 times for 100% tenacity.

Taking a break: When you are victim of a hard cc, you regenerate 5% health over 5 seconds. Slowing effects will heal you for 2% over 5 seconds. Can be affected by multiple instances of the heal.

Swat the mosquito: Each attacks and spells against you grant you 2.5 movement speed for 3 seconds, stacking up to 40 times for 100 bonus movement speed.

Seeing red: Crowd control effects against you grant you stacks of Bullrush. Your next attack will discharge the stacks to deal bonus physical damage equal to your Bullrush stacks. Hard CC give 20-120 Bullrush stacks. Slows give 5-30 stacks.

Bring it on!: Taking damage from more than champions grant you bonus Armor and Magic Resist. Each champions damaging you beyond the first grant you 5-20 Armor, and half that amount in Magic Resist.

Provocation: Getting damaged by an enemy champion gives you the Prococation debuff, the debuff lasts 2 seconds, but is refreshed when receive further damage from enemy champions. Dealing damage to an enemy champion removes the debuff. If the debuff persists for 6 seconds (In other words, you got kited for 6 seconds straight) the debuff transforms into the Challenge Accepted buff. Challenge Accepted makes your next attack against a champion gain 250 bonus range and makes you dash toward them.

While some of these effect might sound powerful, don't forget that you are sacrificing extra damage or tankiness from other rune trees.