Int isn't significantly more effective than matk... it is a slight effect at best. And the effect would be less noticeable if we are talking endgame lukless, since the character would have so much base int already... it wouldn't be much of a % difference to equip a staff that trades ~9 matk for ~9 int when you have 600+ base int.
For instance, with my current equip set (I am 161 and low-luk), subtracting 9 matk and adding 9 int changes my theoretical max Gen to holy weak from 89,922 to 89,968. Now, I am not lukless, and I use a Reverse wand so I have more matk than the typical lukless would, but at that level, you have a lot of base int so the damage formulas tend to look alike anyway.
So... Basically, it's not worth the trouble, unless you want another ~40 damage to a skill that does 90k.
Magic damage formula for reference:
Spoiler!