The only difference between infantry and naval forces is the size of the emitters, ezo core, power source, and barrel length. The principles behind mass accelerators and kinetic barriers does not change with scale, only the power applied.
I was inclined to go on a tangent over professional and scholastic experience with being in the Field Artillery and being keen on applied physics, but then I saw the glaring problem: The game doesn't support your assertion. Look at Sovereign. Look at what I said about what happened. Entire fleets did just what you suggested with the SMG's shooting at the barriers at once... to no effect. The fleets had no discernible effect on Sovereigns barriers. It was Shepard's intervention alone that disabled Sovereign long enough for it to be destroyed. Meanwhile, Sovereign was wailing on those fleets like nobodies business. Now, on to the next paragraph of yours, because that's where I get into the meat of your argument. I do love the taste of juicy meat, especially when I eviscerate it with my fork (of Logic! hehe).
1) The bulk of the citadel fleets were actually deployed at the relays leading to the citadel, the strategy being to keep the geth from ever getting in striking distance to begin with. 2) Needless to say that when Saren shut down the network none of these fleets were able to come back and help the small force left behind which so became engaged with the geth fleet that Sovereign brought with him. 3) The only fleet to focus on Sovereign was the human fleet which contained between 2-3 dozen ships of cruiser and frigate class. 4) As for the quarin fleet, they are firing swivel mounted mass accelerators that I would be surprised if they were even 30 meters long. 5) A frigate should have somewhere near 100-150 meter long spinal mounted mass accelerator providing them much greater firepower.
1) Well, that failed miserably, because look who got to the Citadel with complete surprise and did tremendous damage that nearly decapitated the entire Citadel leadership!
2) You wonder how they even got through to the Citadel to begin with... The Council really should have thought their strategy through a lot better.
3) According to the War Assets, you're wrong: descriptions for several of the main human fleets implies that multiple fleets did indeed participate in the battle (and dreadnoughts were mentioned to be present). As well, you can actually see several Council ships also aiming at and shooting at Sovereign. More than one fleet was wailing on one Reaper. And until Shepard arrived, that Reaper was casually dismissing their fire and blowing them to hell.
4) They were also firing a lot more than just coaxial point defense turrets (those are standoff weapons by the looks of them, designed to target close-in forces and missiles) from more than 5 ships at one smaller Reaper. That's hundreds, potentially a thousand or more ships firing multiple heavy volley's at one smaller Reaper, and it tanking no less than 4 full salvos before going down.
5) Yet still nowhere near the scale of magnitude of a Reaper or even a Dreadnought. Against a Reaper, you might as well open the airlock and throw rocks at it.
Shock attacks do tend to break moral which would make the war easier, but they are also often the mostly costly option.
Speaking from professional experience as an officer in the United States Army, this assertion is true when you have a substantially smaller force in comparison to your attackers. It falls under when you substantially outweigh them in number and firepower. Look at the opening moments of OIF back in 2003. The Iraqi's knew we were coming, and they still couldn't do a damn thing to stop us from steamrolling over their forces in less than a week. We were in Baghdad in less than a week. And the disparity between our forces wasn't especially large. They were armed with mid-late Cold War era tech, and we had the modern tech, and we completely wailed on them. As I said in an earlier post, the disparity between the Council races and the Reapers is a lot bigger. The Council Races are the equivalent to late-industrialized tech found in the interwar-to-early-WWII, compared to the modern assault forces of the Reapers. There isn't a hell of lot of stuff you can throw at them that they won't repel without trouble.
The Reapers have both. As I said, see what happened when just one Reaper attacked the Citadel? I'd wager that two full-size Reapers would be able to take it. Granted, I'd be assuming the Reapers would be using more numbers than that. But the costliness of the assault is completely undermined by the sheer scale in how powerful the Reapers are compared to the others.
The reaper fleet split in 2 and launched attacks against Earth and Palaven while sending off raiding parties to attack smaller worlds and keep the other forces off balance. Assuming they are not holding back the vast majority of their fleet for no particular reason they may have sent up to 1/3 of the fleet attack Palaven by surprise. What does that say about there inability to take control of the system, and even weeks/months latter the Turian fleet is still fighting back and contesting the system? And of course I know they are firing back, but we do see reapers fire and they do not fire significantly faster then organic weapons, destroyers only have one gun and sovergien class seem to have a bit of trouble lining up multiple shots.
It makes no difference how large the Reaper fleet divides itself. And from looking at what happened at Palaven? What was 5 or 6 Reapers in orbit facing a large portion of the entire Turian Navy? And casually smashing it? The Reapers seemed to be focusing a lot more on actually subjugating the planet than taking on the assaults of Turian fleet, especially when they adapted their skills to them. You hear it everywhere, with how bad the Turians are having it. And I doubt more than a few hundred Reapers attacked either Earth or Palaven. The rest of the Reapers, you guessed it, were needed somewhere else. There's a lot of planets to conquer, better get to it. The Turians strategy is mostly on irregular warfare and not engaging the Reapers directly. Though they are keeping the Reapers occupied, they also acknowledge that they're not even so much as scratching the paint on the Reapers. As well, the Reapers are more interested in the harvesting phase of their invasion than the fighting part. The Turian resistance is acknowledged to be largely ineffectual.
Also, your assessment is inconsistent with established lore, given that Reapers are acknowledged as having far superior aim, range, and targeting ability by the codex compared to any Citadel fleets. They don't need to fire as fast as the Citadel ships. They're in a tank getting peppered with machine gun fire. That's basically impunity for them.