The level differences in the IB aren't all that apparent.
I was doing about 1 damage per round difference between a level 30 and a level 26 (I'm 28) on a pulse rifle. Not all my weapons are maxed though, but having a maxed legendary machine gun makes a world of difference.
In general grenades feel somehow a LOT stronger, and there are just a lot of better players in general playing the IB, hence the perceived increased difficulty. I saw a pretty good player I regularly run into wrecking everyone's shit at level 28, there's still a large difference if you're a considerably good player.
I like the new connection bars the patch brought it, but the servers are still connecting people with red bars into a game full of greens.
Also if you play in with a fireteam you will most likely win.
Somehow I was put into that shitty tiny ass map on Mars (red sandy exterior, base with 2 large ass doors) non-stop. I played it over 6 times in about 2 hours. I don't know if they've messed with the map rotation.