They were easy to defeat with the right tools in the previous games but the hit detection and landscapes are broken in 4 which by extension breaks certain enemies :\
I'm just bitter because the stealth was broken for me and I found the game really boring.
Landscape issues with invisible collisions (like when shooting around corners) has always been a major thorn in these games' sides. I honestly don't know if they improved this aspect in 4, or if I'd just gotten used to it at this point. However, landscape interference with hit detection when it comes to explosives is fucking atrocious in 4; I've had so many enemies completely evade damage from a mini nuke explosion because they were a foot higher on the terrain or were 'shielded' by a fence post that I don't even waste time using a Fat Man anymore.
Stealth in and of itself seems okay in 4, but they completely ruined Stealth Boys to the point of uselessness. How long do they last, ten, fifteen seconds? Just enough time to get right in the middle of things and have it wear off. The legendary cloaking prefix isn't much better, and once I got the bug where the visual effect became permanent (either on myself or one of my companions, can't remember), I swore it off for good and didn't particularly miss it.
My issue with stealth is that enemies always instantly knew where I was no matter how far away I was and regardless of the fact that I was using a silenced weapon. I got mini-nuked to hell and back so many times when I was like a mile away from the target. ---