Quote: The big constraint against the 4th shield is power consumption. I often can't find the power to run it even at max. 8 power in weapons, 5 in engines, 2 in each of cloaking and hacking and drones (or teleporter or MC)... that's already 19 leaving only 6 for shields even at max reactor! Backup battery and zoltans can help of course, but I've had several cases where there's no power available to run the 4th shield by any means.
Many weapon configs don't require 8 power, and similarly cloaking can be 1 power for most of the flagship if not all. If you actually do have level 4 shielding, one of the strongest plays is to just hack RFS missiles and cloak/hack chain them (1 power cloak, 2 power hack). With weapons 6 and that system setup you're spending only 9 power, so you have enough to power the shields and use usual oxygen swapping into engines as-needed.
Power toggling defense drone is worth doing vs RFS if you're rich enough to have marginal evasion upgrades otherwise, since reactor is capped. Otherwise most toggling is between that, oxygen, and engines. While you *can* toggle shields off after 1st layer gets hit with pause buffering and dump that into evasion, I hate doing that because it's tedious and almost never necessary. Only for rough early sector situations.
I agree with you that the artillery beam sucks, for many reasons actually. Power hungry, undue expense to upgrade, works poorly with standard weapons (flak artillery is still bad, but less bad for this reason), and worst of all opportunity-costs you out of a more useful system. I'd consider it an advantage if it could be sold, similarly to how one should treat crystal vengeance

Quote:I can see this point but I'll state my case as well. I think the BL3 is better than IB2 specifically against 2-shield ships. I think I deliberately traded off performance in sector 2 for better in sectors 3 and 4.
IB2 fires ion/3.2s with expert gunner (likely you'll have one by sector 3 even w/o grinding, if using IB2). BL3 takes 15.2s to fire also assuming expert gunner. IB2 will just barely fall short of firing 5 shots in the time it takes BL3 to charge, and will remove 2 shield layers after 3 hits.
Not only can IB2 then hit weapons directly, but if you have any secondary weapon (cheaper to hook up given 3 power), hitting the weapons with that weapon first then tagging it with an ion will guaranteed drop two enemy weapons, and the ion buildup remaining on shields is long enough that fast charging weapons can get a 2nd shot off on something else before enemy ship restores shields. This double-tapping effect on weapons is how I ran that ion-heavy lanius ship from sector 5 to the flagship w/o taking damage.
In your case I'd have likely sold BL3 rather than IB2 to grab dd1 or maybe a low power weapon. IB2 is a better weapon overall, even for shutting down enemy weapons before they damage you. Depends on what else is available in the shop though, I usually try to pick up at least a heavy laser or something. The alternative is more ions, enough to overwhelm evasion + lock down piloting + weapons permanently (or piloting + cloaking --> shoot something damaging into weapons or cloak/hack them).
I actually have the opposite conclusion to yours; IB2 is still better vs 2 shield ships and starts being too outclassed vs 3 shields by itself. The reason is that you get more support systems on enemy ships and more opportunity for chained miss trolling on 3 shields...but both of these weapons are inadequate by themselves vs 3 shields and need more weapons + systems to deal damage. BL3 can at least do damage but vs evasion there's too high a chance you hit for 1 or nothing vs 3 shields. 2nd/3rd weapon are cheaper to attach alongside IB2 however.