It's a tricky game to balance, really.
Every encounter has to be winnable Singleplayer and offline mode. So, lets the the enemies are all 100% of their efficacy at this point. You summon another player and they're down to 50%. But you can summon TWO people bringing them down around 33%! But its not like the enemy can target and engage 3 players at once, either. The player the enemy is attacking can just block while the others are free to lay in the hits. So the challenge with 3 players is more like 10% of what It originally was. Easy enough?
So, how do you balance this to actually keep the game hard? Do you scale the enemies stats up based on the players in the world? Spawn more enemies based on players in the world? No, neither of these are happening. Changing the AI to accommodate the extra players is the best option I can think of, but I don't think this is happening, either. The monsters will just get their asses kicked by the three of you. All we know at the moment is FromSoftware is messing around with the summoned players being unsummoned after killing a certain amount so they cant carry you all the way, but its all still undecided.
If you take all this into consideration then its obvious you'd never need an "easy" mode because you can just summon people to carry you though the whole game. If you'd never worked this out then it wasn't the combat difficulty that was the problem - it's just that you didn't understand the underlying game mechanics applicable to your success. Making the enemies hit for 1/4 damage wouldn't help you learn to summon people any faster. It's a suggestion only someone who doesn't understand the game would make.
FURTHERMORE, having an "easy" mode would separate players into two groups who couldn't interact with each other, which would make finding people to summon in order to make the fights more easy a harder task. All the "easy" mode noobs would be stuck with only each other to summon when they could have just summoned a pro who'd remove the challenge entirely. I reckon I could win dark souls without ever killing a boss myself just through summoning players!
