I think that whilst the corrosive cloud was active the drop rate was higher.
Or at least it was in a roundabout way because “new” Titan wrecks would have a lot more stuff spawning in at once than when it becomes freely accessible. Thus, more chances for the TDC to appear even with its (seemingly) lower spawn rate.
Also, seeing those posts concerned about Thargoids… you actually really needn’t worry about those at the wrecks. I don’t know what weird thing’s going on with their AI there but the Interceptors don’t attack anything until shot at, usually by AX NPCs… and if you then keep a distance, especially while a swarm is out, you’ll be able to avoid combat entirely. Scythes (the ones that appear in pairs) won’t bother you unless you have some form of human “cargo” or the bio pods floating around.
Both will also either be killed or lured away from the wreckage field by the same bots that attack them, while it also tends to make pirates hop out, so that’s another bonus. At worst, just do rounds away from the Thargoid, but I’ve never been attacked by one a single time there [after the Scouts disappear when the caustic cloud dissipates]. And I’d say I would’ve been noticed by an Interceptor marked as “hostile”(red and being targetable as such) passing within a kilometer of me, though your blood pressure probably isn’t happy when it’s a Medusa.
Of course if you are able to go to Sol and are that concerned, then just visit there. Supposedly the AX NPCs will even act as security stand-ins if hassled by one of the pirate nuisances roaming.
As for my experience gathering the things… well, it mirrors more or less what others have already said. Sometimes I can get one within minutes, maybe even three per hour, other times I could spend hours searching and just… never find one until I get bored and move along. Fortunately I’m currently in no need to do more collecting and have a few spares on my main account’s carrier if the need does arise.