The basic idea is good and it sounds like you are adding in some nice details to flesh it out. I have some minor concerns though and some comments to help flesh it out more. 1) It sounds like fighters in defense mode can engage 3 guys. That sounds like a lot. I can see this for an experienced warrior but for a base ability it sounds like too much. If your parrty had 3 ranged specialists than an NPC warrior could tie down all your melee guys. 2) When engaged you should still be able to move a little. It sounds like you are planning something like this but the details weren't there. Since movement is taking place in real time I would recommend actually making the movement rate slower until you are disengaged. You can force the disengage at any point though to get full movement back but provoke an attack of opportunity. You mentioned forcing an opponent to stop when engagement starts. Maybe the slow move effect could replace that and give a similar effect? 3) Please add plenty of abilities to manipulate attackers and defenders that are engaged. You mentioned some of these for the different classes but add more. A more experienced warrior should be able to slowly move the opponent back and slowly circle around him for instance without provoking an attack of opportunity. If you have a shield you can try and push them back. 4) Have the engagement radius be based on the weapon length as well as the experience of the fighter. Small weapons could get accuracy bonuses to make up for this (easier to react to a sudden unexpected movement). 5) Not so sure about the Grimoire Slam ability. The effect is fine but the picture that name brings to mind is a bit goofy. Maybe just give it a different name. From the comments above it sounds like some do like it as it is though.
1) Level scaling - ruins RPGs in my opinion 2) Guns - looks like I won't get my wish on this one but I hate guns in fantasy settings. Save them for more modern settings. 3) Few skills/customization options - I want to make the character I want, not some cookie cutter character. From what I've read so far I think this will not be a problem. 4) Boss battles where my carefully laid positions are overriden, My thief becomes unhidden and my mage is standing face to face with a big bad demon when he was originally way in the back. Do not force move my characters just so the boss can talk to me.