I think the lower TTK, restricrted shield regen and higher overall speed of the game have made it much more difficult to stay alive for long periods. Used to be that if you played smart, you could string together a bunch of kills and survive firefights, run away and recharge your shields and stay alive for quite a while.
Now I'm finding that surviving a 1v1 fight usually ends up in me dieing anyway, teammates can get to the site of the battle so fast now and your shields don't recharge as quickly as previous Halos. Also seems like grenade can be thrown much farther and are more "bouncey". All of this feels like it adds to an increased number of deaths, which probably evens things out a little more.
I gotta say I like it more. If you set up shop in an area in previous Halos you could really dominate with your shields recharging quickly and whatnot.