You could/should make more use of Ratio per Rank Up when balancing Tanks

For example:

W - Twisted Advance:

• Damage: 50/75/100/125/150 --> 50 at all ranks
• Damage Ratio: 0.4 Ability Power --> 0.4/0.475/0.55/0.625/0.7 Ability Power (+7.5% per rank)

If Maokai ranks up his W second he forgoes damage in exchange for Tank qualities (CC and tankiness via lower cooldown untargetability). If he ranks it up last his damage falls off after level 13 and he has to rely more on his build and team to perform his role as a Tank. However, if Maokai forgoes Tank qualities from the start by building damage he doesn't lose so much because the Ability Power ratio is increased with rank.

In this example Maokai would need 333 Ability Power to break even.