4E Lessons for 5E

[FatR]

One I'm actually sort of surprised nobody has brought up (and one which may generate some backlash)

The player base, by and large, does not want a perfectly balanced game. 

3.5 was unbalanced; 3.5 was also very successful.  4e fixed most of the balance issues--and was not nearly as successful.

      Or... it might have something to do with 4e far-from-perfect balance being bought at the price people weren't willing to pay, like reduction of the gameplay to the single dimension of HP attrition (that happened way too slowly, too) or having to deal with, like, 100 goddamn pages of errata.

[kitep]

More from earlier editions (I've never even played 4), but here goes:

I have a love/hate relationship with save or suck spells.  I can love casting them, but it can worry me to be on the receiving end   There are times I can even hate casting them, as it means what should be a big serious fight is over quickly and easily.  The old "initiative wins" thing.  Very anti-climatic and un-fulfilling.

It can be bothersome that what should be worrisome isn't.  Kidnapper gets the drop on me and has a heavy crossbow pointed right at my heart, with a readied action to pull the trigger if I don't cooperate.  Average damage 5-1/2.  Average crit damage 11.  Might be a bother at level 1, but not at higher levels.  Even if he's got it pointed at a level-1 commoner, I figure it'll just take the guy down to negative hit points, not kill him.

[kitep]

Since I said something negative in my last post, I'll even it out with something positive.

I love the level-up system.  I've played other RPGs (Champions, Torg, Call of Cthulu, etc) where you add things little by little.  Just not as fulfilling as leveling up.  Of course, I tend to play spell-casters where leveling up really counts for something (at least every other level).

[linklord231]

It would be nice if they implemented a system kind of like in 4e where you add half your level to spell attack rolls.

Specifically, I'm thinking of this:
In 3.5, spell save DC's kind of taper off toward higher levels - the only way to increase the save DC is to increase your casting attribute, which is tough to do after 18+2 (racial) + 6 (item) + 5 (tome) + 5 (levels).  On top of this, save DCs tend to remain fairly static until you buy the big stat boosting items, and then they jump a lot.  I think a system in which you add half your level to the DC to resist spells would be beneficial to both problems, because it would smooth out the big jumps by increasing them in small amounts every 2 levels, and would continue to be relevant into epic levels. 
I was disappointed when my epic cleric's favorite spells suddenly stopped working because I couldn't increase his save DC's as fast as the monsters' saves were increasing.  Making the formula something like 10 + spell level + half your level (plus spell focus et al) would make higher levels less of a race to find more and more obscure bonus types in order to stay relevant.