BFG and rocket launcher are the weapon of choice against Arch-Viles. They raise corpses (even before they see you - I consider that a bug, but what do I know?) and hide behind, so you need an area of effect weapon to get through to them. And double shotgun is not good enough - it is a short-range weapon! You'll just die trying to get to them...
Revenants do not pose that much of a problem if you do it properly. First, do not hesitate to use Rocket Launchers - they drop enough ammo for you to restock. Second, Rocket Launchers push them back, which is a huge plus. You have time to reload while they walk back towards you.
One of the tactics I found useful: when you have Cateye(2), you can kill pretty much anything but fliers (most notably Cacodemons) if it stands behind a stream of lava. Stand just outside their field of vision and shoot with your weapon of choice (two pistols, chaingun, plasma rifle, etc.) while they stand there helplessly. Even Barons and Arch-Viles do not dare to wade through lava (only demons do). Just be careful if you are using rockets - you might destroy a piece of wall and open a way around that lava patch for them...