Heals and shields are 5% stronger and increased by an additional 10% on targets below 40% health.
Aery on Rakan allows you to repeatedly apply the shield with [Q]'s heal and a spaced-out timing of both [E] shields, for tons of damage mitigation.
Nimbus Cloak synergizes fantastically with Rakan's [R], empowering your ability to hard engage a skirmish/teamfight at will.
Rakan makes great use of the bonus Movement Speed from Celerity to get around the teamfight and the extra AP from your [R] movement speed means your engage damage and [E] shield's are that much stronger.
Scorch allows you to poke and trade aggressively in during the laning phase if you are able to land [Q].
Bone Plating's burst damage mitigation helps you to survive and withstand incoming damage after a hard-engage so that you're able to get in and get out.
Revitalize is fantastic on Rakan as is empowers the heal from your [Q] as well as both shield's on [E] and your passive shield.