I haven't checked the full landscape recently, but it seems you can "opt-out" of most datamining sites now which would make catching cheaters several magnitudes more difficult then it was in the past. You would need to have personally played (and tracked) an exorbanent number of hands against a cheating opponent to be able to deduce that they are cheating, and that is if they are being blatant about it and not trying to fly under the radar.
That's true at some mining sites, not all.
sharkscope isn't as much a mining site, if that's what you're using for reference, unless perhaps you're using their HUD. They're most widely used as a tournament/SNG results site, and upon request from Stars they had to allow opt-outs years ago. They've since extended that option to players of some other sites. Stars forced PTR to stop mining or allow opt-out or be sued into oblivion -- to my knowledge no other
poker site has taken that aggressive of a stance against dataminers. The rest tolerate it silently.
As to HH databases, you seem to forget that:
(a) regs have millions of hands in their own databases,
(b) it doesn't take that many hands to identify many unusual patterns, and
(c) they shared their HH's and/or analysis with each other in the bigger profile cases (e.g. potripper) to create even larger pools of hands to analyze.
While the OLP landscape has certainly changed somewhat in the years since, HH analysis is still the players' last line of defense against game corruption, whether it be by the site or other players.