I play on Madness mostly, sometimes Insane. like others have said, you have to prioritise stun resist (and on madness, confusion resist), and tbh, as many other resists as you can. you also need res penetration and a bunch of other things.
so basically, it is a matter of continual improvement of gear, to be prepared at any time for any eventuality.
I do however make sure I have these things, especially if my current gear is not up to scratch:
1. items to increase light radius - critical on higher levels to have 10+ light
2. gloves of dispersion or rod of annulment
3. underwater breathing (duh!)
4. belt or lamp that makes you undead (=3 too), as sometimes it is a huge help
5. high res pen items, if my res pen is not high enough and I come across a 70+% resist creature (of which there are too many

)
6. gear to give high APR (as in 50+), for when you get 100% armour hardiness and 100+ armour enemies
7. if possible, an amulet/boots/rings that can give 100% teleport resist, as in some scenarios, being teleported around = death (against paradox mages).
you'll see I dont use activable items, other than 2, because normally you're dead by the time the talent on eq coolsdown after swapping. but other players make greater us of these.