Spellcasting is grossly overpowered in PnP compared to melee. Nerfing spells was unavoidable, and of course a good decision.
To prevent many CC spells from being lackluster, they got something that could be interprated as a buff to make up for that. Mind you, they might not allow the same of creative thinking out of a problem but they are certainly more powerful in-combat spells. In other words, they act differently than they acted in DDO. Saying that it's "further of a nerf" says nothing about their power level. However, the fact that many CC spells have been considered overpowered and have been nerfed
before does harm your argument severely.
Just to name a few, Fascinate, Charm Person and Suggestion all got good in-combat buffs compared to their PnP version.
I challenge you to show me a video supporting the claim you need three whole minute of Fascinate or more than a minute of Flesh to Stone.
That reasoning might be applicable to Suggestion or Charm Person, but not to Fascinate nor Flesh to Stone.
To answer your question, it's acceptable in PnP because there is a DM and because quests cannot be repeated. That's the answer.
In PnP, it's the DM's job to ensure the players are having fun and he can respond to that in real time. Finding a smart way around the encounter is fun. It's like solving a puzzle. If the DM sees a way to let you have fun, he'll let you have fun, adapt and change his plans in a way to ensure the game's still fun.
In DDO, Turbine is the equivalent of the DM but there is no way for them to ensure that you're having a good experience in real time. They can only improve our experience by changing the game. Thing is, if the players are overcoming game mechanics, even if it's by smart play, it impacts their gameplay because it means the quest is not challenging. That's not a problem if they do it once. Finding a smart way around a problem is fun, after all. But, they'll repeat the quests several times and pass to other players. Finding the solution the first time is fun, the the reduced challenge the other times are not. In this case, the fun problem solving is dwarfed by repetition.
That's why.