-400 or more less online today
2493 online which was >3k a few years ago.
I know this might seem like a meaningful metric, but it's not. What matters more is how many of them are out of town, how many are using trusts, how the instances are structured, how large the groups in individual instances are (data increases exponentially), etc.
It's reasonably likely that more instanced content is going on now than a few years ago (ambu and omen have become easier, sortie has been added in, more people can tackle odyssey). We also don't know if the resources used to host instances are dedicated by server, or in server clusters, or shared entirely. We know SE has changed their topology.
Without direct information, I think it is difficult to say. Effecting certain characters more than others makes it more likely to be a software capability+prioritization issue, rather than a network capacity one, imo.