That's certainly the obvious choice, although I can say from experience that in spite of conventional wisdom, I have always noticed the difference between no fitness and three fitness in Gold, even on 500 Health/shield characters.
That's because the "conventional wisdom" regarding fitness is mostly rubbish, IMO. And I will add that 990 shields is practically just divined from the ether and isn't based on much of anything that makes sense.
Personally if I am going for shield number targets, I think about the hitscan enemy that is consistently the most irritating with 3 shot shields to death burst: the Phantom.
Phantom base hand thanix damage is 250. OOC damage modifier 1.4x, Gold difficulty is 2.5x, and Platinum is 3x. So on Gold you are looking at 875 damage per shot, and for Platinum it is 1050. If you aim for total shields after consumables right above either number, Phantoms will only be able to healthgate you at most since shields will take two shots to gate (at least from full shields).
Otherwise I don't find a huge amount of utility obsessing about other hitscan enemy burst damage because whether or not you get a full burst or if you are hit by multiple units is hard to predict beforehand. Coming up with a target for shields would end up depending at least as much on host fps and character speed as enemy burst damage for most of these units. Hence why AM3 is better across more characters at lower fps than higher, and in general shields (and fitness) has the lowest value at low fps on maps with tightly spaced cover, and increases as fps and distance between cover increases.
For preset to Gold Reapers only, you could try to think about total Banshee DOT or potentially Ravager acid, but that isn't usually all that important except mainly on Geth with HM active.
Geth Hunters were mentioned above, but if you start worrying about their damage per burst, you will need a lot more shields since they run the GPS. Fortunately, they fire relatively slowly between bursts.