I carry all of that stuff, plus a bit more! As far as I'm concerned, the questions you need to ask yourself are:

1) Do I know how to use the tools and parts that I'm carrying?
2) Am I touring in a location where getting help or a ride will be difficult?
3) Will the bike be completely disabled if I can't repair or replace a particular part?
4) How likely am I to use the repair supplies I'm carrying compared to the weight of the supplies?
5) How easy is it to obtain repair parts or tools that I'm not carrying?
6) How likely am I to miss an important deadline if my bike breaks and I don't have the appropriate tool or spare part?

Here's a list of stuff I typically take with me:

Pedros Tire Levers
2 spare tubes
Standard patch kit (tubes get patched at the end of the day)
1 spare tire (700x28; the smallest that will comfortably fit my rims)
1-2 tire boots (a.k.a. dollar bills)
Spoke Wrench
Chain Tool (Park CT-5)
Multi-Tool
Leatherman
15mm Pedal Wrench - small
Topeak Road Morph G pump
3 spare "master" links for chain
Spare chain links (5-6 links removed when fitting current chain)
FiberFix spoke kit or spare spokes
Brake cable
Derailleur cable
Chain lube
Derailleur adjustment instructions
Cassette lock-ring tool

Most of this stuff packs down pretty small. The tools don't cover every situation, but they do get you much of the way there. If I wanted to remove the cassette, for example, I carry the specialized tool required to do so but I'd still need to borrow an adjustable wrench and remove the chain from the bike to use as an improvised chain whip. My tours tend to have fixed deadlines (read: I have to get back to work) so wasting a day or two trying to get a broken bike repaired can have a big impact on me. As a result, I tend to carry more spares and tools than I might if I had more time available.