If I recall correctly, electronic hardening functions to reduce the effects of meson cannons. And I think high power microwave as well. No, it's not armor, but it's better than nothing. I'll admit, until I incountered the Star Swarm, I usually skip that series of research tech.
I would double check with Steve, but IIRC the hardening does nothing against mesons.
The other problem with meson's is that they only do 1 point of damage. Against larger systems this translates as needing multiple hits to garantee knocking them out. for example a ship engine has a HTK of 2. This means each time a meson hits, it only has a 50% chance to destroy the engine. A quad 15cm weapon turret has a HTK of 8 which means each time you hit it you only have a 12.5% chance of destroying the turret. Missile launchers have a HTK of 1/2 the size of the missile, assuming no reduction in size, Magazines can be designed with multiple HTK, Power plants can be made larger with increased HTK, and larger power plants can more efficiently use internal armour, etc. There are plenty of systems on a ship that are only 1 HTK (hit to kill), but there are ways to make a ship harder to effect with meson's. Another thing to remember is that the damage allocation chart is based on the total hull spaces that the system takes up on the ship. The more of these large systems there are, the more likely they are to being hit in the first place. All of this means that a large ship with multiple large systems, and redundant fire control and sensor systems is fairly hard to take out with mesons, especially if the engines and power plants have reduced power outputs to make explosions less likely.
I will admit however that Meson's can be deadly, I prefer to play with them as my primary point defense weapon and have liked the results a lot. I have lost a lot of ships however when they could not close into their range before being pounded appart by other weapons. It is one of the reasons that my prefered long range beam weapon is torpedo's. Between the two systems it is very hard to fight me in beam range, and with all the small meson turrets that I have, missile attacks tend to get torn up fairly well.
In response to the coment above about shields being under powered compared to armour, I actually have to disagree. LOW tech shields are pathetic. By about the point that shields give 3 points per hull space they become fairly usefull. At higher techs they are very effective at preventing damage from attacks that are not concentrated. If the engagement is at long range, the percentage of hits for beam weapons is fairly low, and even small ships are able to regenerate a couple of points of shields between each salvo. This adds up to a lot of damage that never gets through to the armour. With incomming missile attacks, if the defenses can thin out the strike so only a few missiles get through each time, then the shields do the same thing. Against someone able to get massive attacks through shields are much less usefull, but against fairly equal oponents they can be crucial. I have play tested this a couple of times fighting myself with equal tech and size fleets and this was the result.
Brian