Before the changes to Master Yi's Wuju Style

You would need to have 225 total AD to allow Wuju Style to deal 75 true damage on-hit when maxed: This is the same amount of true damage that Irelia's Hiten Style is capable of dealing when maxed.

With those changes, you need at least 140 bonus AD (at level 18 this means at least 251 total AD, value can be lower at lower levels) to match those 75 true damage. This is taking into account the change to the base damage.

Keep in mind that Irelia's W stop scaling when maxed while Yi's E only continues to scale the more AD he has. With the change, however, it is probably that he will need to build another AD item if he wants to reach that value, taking into account the passive effect on Yi's E, and the fact that, because it is bonus AD now, Sterak's Gage no longer affects Wuju Style's true damage.