I find one of the big issues with Strategic Resources in this game is that big armies using them aren't really required. You can accomplish almost anything with a Carrier with 3 Fighters and 4 Battleships, meaning your deathball can run off a single oil well. Similar story with Frigates - 6 Iron will supply enough for a 6 Frigate + Privateer fleet, and nothing else needs Iron at that point.
4 Horse Archers will get a lot done, and all you really need at the front of a Composite or Crossbow rush is 2 Swordsmen/Longswords.
You can get an Ideology off a single small supply of Coal.
The only times you're really screwed are when you have exactly zero of a resource. Some other times you have to make minor tradeoffs (no buying Hydro Plants when you're short on Aluminum, fewer factories if Coal-strapped... but you only need the coal once to build the factory and they'll run forever without it), but overall you won't suffer militarily unless you have zero of anything.
In future versions of Civ I'd like to see more emphasis on having more Strategic resources. Perhaps the further into the game you go, more complex units require more resources. Tanks could require a couple Iron plus some Oil. In WW2, embargoing Japan's supply of iron to make steel was a pretty powerful move. This way, trading in strategics could have some value too - I think the only time in a dozen games recently I've ever bought any strategic was to build Factories, and once I bought Iron so I could upgrade Jaguars through Swords and Longswords to Muskets.
