There is already some behind-the-scenes limitating of DWeb going on there. It applies to most spell casters, but in particular to the DA, HT and Corsair, so Protoss get the brunt of it.
The modification is that when you mass particular spell casters, past a certain limit the units spawn with a lower % of energy, instead of the default 100%. This means there are diminishing returns on adding extra units. See reply #33 in this thread, it seem that corsairs only get capped after the 7th one, so I could make this stricter.
Did the terrans try going for 4 science vessals each, with EMP? That drains energy and shields. Also ghosts for lockdown on corsairs and reavers.
As for limiting the units, I don't really want to do that. At the moment the units that are limited are spell casters, where massing them is completely OP (like queens, ghosts, defilers and science vessals) and void rays / roaches because they have special health dynamics. If I place a cap on protoss air, it really gimps them too much, especially against Zerg.
So re-balancing is probably the best bet. Options:
- Increase cost, I was thinking of putting the price up by $30 to $680 anyway
- Reduce corsair spawn rate, I believe it is 1.5 at the moment, drop to 1.25?
- Reduce corsair damage - they already only do 6, and most air units have 4 or 5 armor, so hardly do damage as it is
- Reduce corsair armor - I think they're 4 at the moment, drop to 3 would seem reasonable
- Reduce corsair HP/shields
- Make the corsair energy spawn harsher, something like starting at #6 and every 2nd corsair thereafter, instead of start 7 / every 3rd.
- Increase price of dweb, but it already is pretty expensive at $320 I believe and this is only a 1-off hit, and corsairs are pretty worthless without it. Putting in some of these other changes may require the price to be lowered to help compensate, anyway. It is already pretty expensive to pay $850 for a fleet beacon to have access to the upgrade in the first place.
I don't really want to touch the scout too much, because protoss air is already very difficult to balance: corsairs need to do low damage, due to huge splash, but this makes them weak vs armored enemies. Scouts do explosive damage, and have 2 separate missiles so suffer a 2x armor penalty on their attacks. Carriers obviously need their interceptors to do small amounts of damage, which again makes them very penalised by armor. Arbiters hardly ever actually attack, and have very slow cooldown, and it is already being used as mothership in this map (hence why the mothership 'special attack' is so strong, to help counterbalance other weak protoss air).
None.