What do you mean? Going like full 21 in the Offensive or Defensive Tree? If you go into Offense you won't see any major damage output unless you really put some damage items like if you were building an AD carry, I use a pure Tanky DPS Irelia so that just doesn't fit my playstyle. The reason I don't go full into Defense is that you don't need that extra tankyness really, you get pretty tanky by having items and by that you just have to farm which is very easy as Irelia. I opt going into Utility because it really benefits Irelia's kit, everything there is really useful and you won't/can't get some of those effects as items so I think it's better. Like I said before it comes down to preference, this is my way of playing Irelia and this is the exact stuff I use, you can use this as a guideline and make some changes that match your preferences of course ;)

I don't know why u get disvote but this is perfect build same as guide just fix masteries you should have protection or ofensive!Good one +1!