Conditions and bookkeeping.

Ok, so this is a general one but I'll use a specific example. First, let me preface by saying, I'm a big fan of 4E combat. It's deep and tactical and rewarding to do well. It takes a long time but can be fun the entire time if done properly.

Having said that, one of the things that I always found cumbersome was condition tracking, especially at paragon and higher. All the rules that had minor variations to provide the proper balance were brain numbing. Some powers had save ends. Some lasted until the beginning of your next turn. Some lasted until the end of your next turn. Some lasted until the beginning of your opponents next turn. Some lasted until the end of your opponents next turn. Some could be sustained with a minor. Some got progressively worse with each failed save.

Tracking, outside of a computer tracking program could get pretty daunting, and IMO didn't enhance what was already a rewarding tactical experience. We had lots of tools. We used colored tokens and pipe cleaners. I had a nice magnetic combat tracker and even a white board and folded "tent" cards on my DM screen. I had hand outs with all the different conditions and we played them like cards on the table. No solution felt smooth. It was always painful.

So when I was prepping the Troll for our upcoming playtest, I noticed that these types of condition tracking are returning. Basically, when the troll takes fire or acid damage, his regen stops working until the end of his next turn. Please, find a better way to mechanize this. Tracking conditions this way might be fine for one character or monster in a fight, but when designers get the OK to use conditions this way, they will use it alot. And like 4E, when you get into higher levels, tracking will be out of control again.

Or, if you're not willing to find a less cumbersome way to deal with conditions, at least push this type of condition tracking into the optional module for tactical combat. So only those who are actively seeking out that experience need to deal with it. (which, in many cases, will be me, but not always, not by default). 

Instead, I suggest having a simpler baseline. Using the troll as the example, replace "fire damage removes this trait until the end of the trolls next turn" to something like fire damage simply can't be regenerated. Or, more than 10HP of fire damage halves regeneration for the duration of the combat. Or simply that the coup de grace must be made with fire. But please think very hard before you unleash this style of condition tracking into the most basic version of the monsters.