You don't really need that many level 7s. Agi Dhans need MR, DB, Silence, and Boost and Avoid can be left at level 6. Str Dhans need PC and MR. DB can be left at level 1. An extra 10% Strength can be matched by taking your +5 weapon to +8. Just get PP and DPP to 6. That extra damage you get from going from level 6 to 7 will hardly ever make the difference between a kill and your target escaping.
With a Str Guard you don't need any level 7's at all. Just get RM, CS, CS, Roha's, SS, and a few other things to 6. Damage-wise, you'd be missing 8% Str, 10% Weapon Attack, and 5% More Melee Attack. The extra 1% from OS is negligible. You'd have to be attacking something like a boss for it to make any real difference.
If you completely ignored IM back then, you'd be missing +30 all stats from costume, +40 all from Gold Trophy, and +20 from General Talisman. That's +90 All stats. This absolutely makes a difference, but look at all the stuff you can get within the actual game. There's the +20 All stat talisman from Kasa, the +15 All stat talisman from R5 talismans (Piece of ____), dual-stat weaponry, Eyepatches and Earrings in-game that are better than the ones on the IM, and reinforcement. The key is to get the permanent stuff in-game. It makes the difference between people with IM equipment and people without it, less decisive on who wins in PvP/PvE.
Of course, what I said above doesn't matter at all in 2015. The difference between people with a big budget and those who didn't became bigger and bigger over time. I remember when I still played on my Psy Healer. I was 4x and this Agi Dhan was going around rpking. That's usual, he was critting 900s+400 without Almighty, what was unusual was the fact that I could root him. Normally, he would have to be at least high 5x or 6x to deal that much damage, but no...... he was using 4x Spirit of Sloth. They were accs exclusive to the IM that gave +40 Str, +40 Vit, and +150 Melee Attack each. He had an Armene's Dagger, but because of the Melee Attack and Strength on those rings, he easily did 150+70 through my Pluion, while still critting like an Agi Dhan. You may think I'm exaggerating, but watch what these IM accs can do.:
https://www.youtube.com/watch?v=y4IX3LP0tDc
At 43 seconds you can clearly see the 4x Spirit of Sloth.
... and don't forget this one:
https://www.youtube.com/watch?v=iqC1itkkbjo