Higher level Idols are considerably more economical than items.
Having acquired Rank IV idols, items are valuable to boost minion damage if the enemy has no AE or survivabilty if the enemy does.
On the road to Rank IV idols the only items needed are for Mana and/or Demigod survivability.
The real kicker with the so called minion swarm is the vulnerabilty of the General controlling them.
I remember when Generals complained about OP assassins and started beefing themselves up so they wouldn't get farmed so much.
Guess what's about to start happening to all these minion swarm Generals.
Lately I've been playing Torch Bearer, with -55% AA damage from all attackers and the ability to cut down a naked General in seconds, I have absolutely no trouble against a minion swarm.
Regulus should be able to push Erebus out of a lane with tracking and snipe while doing something else.
If you attack 2k hitpoint minions EVER, you are doing something wrong.
I have seen the odd General run off by a Minion Swarm which is kind of hilarious, if the General can't survive a minion swarm how is he going to survive the focused fire of an assassin (the character he should really be worried about) while his minions are doing their thing.
The best single piece of advice I can give is, "Don't go to town without at least one Tower Destroying General and one Assassination specced Assassin"