Board Thread:League of Legends discussion/@comment-5256326-20150323191048/@comment-5602160-20150326232207

Irelia's scalings are indeed very good when it comes to ad/ap itemization. The reason she isn't played this way is because she can't afford to build that way. She will be diving into the backline of teams and needs to survive to make use of her passive and run away from threats after her engage. She's an in and out champion, but will take a significant amount of damage as tankiness (and her passive) is her only real form of mitigation. Additionally, BT is more burst oriented when she benefiets the most from sustained damage from her w with occasional bursts from sheen/trinity procs off of ult or e activations.

With Irelia you typically want to build trinity force (she synergizes with every single component, and needs the additional mana for extended fights), build tanky, then possibly build a daamge item late after the enemy team has significantly stacked health and resistances. If they are primarly MR you go BotRK, if they are armor go Wit's End. Both of these items synergize extremely well with your primary form of damage against champions building health and resistances (w). Irelia also does extremely well with CDR, making items like frozen heart and spirit visage very valuable.

TL;DR Most of Irelia's damage is artifical  and Trinity Force will basicly give you everything you need. That plus tankiness = easy dives onto minions near bacline carries + stun + fight + q = dead backline carry.