I have played a lot of league of legends for the last year. Here a few things I have noticed playing lol, that I think would also be great for DDO.

1. In a recent change one of the support champions has been changed in an attempt to seperate the players whomaster the champion from those who dont. She used to be about standing in the back and healing without interacting much with the enemy. If the change did what it was supposed to do is another question. But making playing a healer-type character more rewarding would also be great for DDO. For a long time I mained a healer myself(I built him very tanky and also tried to support my partymembers by tanking myself if I felt it would help), however after the enhancement revamp I lesser reincarnated him into a tank with 12clr lvls for sealfhealing. I did that because healing is not really needed anymore (no tanks aren't really needed either so I am playing him as a druid tank now with way more DPS) and I never found only healing really interesting. Healers are mainly needed in raids but even in raids most people are selfhealing these days. Even healing a raid is either very boring if everything goes as planned or is very stressfull and even more pot intensive if it doesn't. Making it so it is noticable if the healer is doing a good job would be great but obviously is not an easy task.

2. More important: the focus on interaction of players and enemies. For lol a new map is being made atm. One change will be that the attacks of monsters and especially the biggest monster will avoidable. In lol another problem is when a player can 1-shot another without them being able to react. When a champion is able to 1-shot others they are usually changed in some way.
The best example for interaction between player and enemy(Talking about NPC-actions players have to(can react to) is probably the lord of blades. The lord of blades himself is the most important part, that makes the lob-raid the best one in the game(at least to me and it makes me really sad seeing people do this on enorm ignoring all the beauty of this great quest). I guess I don't have to explain this much more. Some other examples would be the inferno in von6, the meteors in the DQ-raid, the "run it's casting something nasty"-effect in the sany asylum and many more. A recent addition in this category would be the whirling change attack the shadar-kai assassins have(The NPCs being able to spam the ability is a different problem). The latest raids are lacking this kind of event imo (I am mainly talking about fall of truth, temple of the deathwyrm, fire on thunderpeak and caught in the web). Most of the damage in there can not be avoided by reacting to what the enemy does or there is not enough time to react (Yes the "BOOM" debuff can be negated by actively equpping a spellabsorption item...). The mark of death raid does have some mechanics, that force players to react. I presonally feel like the infernos in there are too hard to avoid/ the ways to avoid them is not reliable enough to me, considering the may kill you and will drain your sp (I would prefer if spell absorption was not the way to go there). I also feel like the deathknights would have been a good spot to bring in some lob-like mechanics that force the tank to react and that force the party to bring an actual tank(like the lob did).
Overall I think focusing more on a few abilites and the actual combat, rather than 10+ hotbars, cooldowns, different abilities, buffs,... will be an improvement to any game. Of course interaction outside of combat is also welcome!

3. I generally feel like the patchnotes for lol inform players better about the reasons for changes. I know this is also being done in the DDO-release notes, however I feel like more would not hurt, even tho the communication between "devs" and players seems good over all.
I also think they usually release the patch notes a day before the downtime

That is what came to my mind while spending time with lol. I hope some of this was inspiring and maybe a new LoB-like encounter.