Warlocks really don't need Intelligence or Wisdom. Why would a Warlock need Intelligence +1? Half a point worth of Spellcraft? If you pick Cha for Will Saves like you said, you don't need Wisdom +1. Even if you don't take that feat, +1 Wisdom is only half a will save. And Arcane spell failure is mostly useless for most builds. Plus, we have augments, items and enhancements that can over come just about all of it. So that leaves 4.
Otto's Irrevocable Power has 8 filigrees to choose from, so you're less likely to run into this problem when you more options available to you.