it's a good build, you have will NEVER come without mana , it has good AD , you don't have a great DPS but can do pretty much damage and still survive very well.
I play Irelia as a AD offtank because i always start the teamfights , they target me and with good survivebillity and still good damage i can take down a enemy , ore hurt more enemy's with my ult.
When they see they have spent to much time at me , there team has take a ton of damage, and they target ore people from my team ore they try to run.
Normaly i get alot of assist, and i die more than my team mates,(because they focus me in team fight) but i don't mind, with Irelia you can get alot of last minion hit's and don't be afraid to use your ult at minions to push a lane.