Soul Memory really sucks.
Been in the 15M+ Soul Memory bracket with a few characters and the matchmaking for Red/Blue invasions (both hosting and visiting), arenas, and RSS/Dragon Signs has become a real crapshoot. Too many total mismatches, wherein my SL125/150 character is pitted against one, or more, SL400+ characters that are a real chore to fight. Trouncing someone relying on a "broken", but one-dimensional, tactic (e.g. Monastery Scimitar, Greatsword/Lance Stunlock) isn't impossible when you are on even Soul Level footing. But when the opponent can gouge VIG/VIT/END/ADP, it becomes far harder.
Lots of my matches seem damn near unwinnable; I'm playing at a pretty high level, but my margin for error is extremely thin, whereas the opposition can afford to make many, otherwise grievous, mistakes. Taking down Hex, Avelyn, Buff, Spin-To-Win, Monastery Scimitar, or any other kind of spammer is within the realm of possibility when Soul Levels are somewhat even. But when they can attack with all of those strategies, fast roll with 14+ i-frames, pack 3000+ HP, and 1.5x the amount of stamina your SL150 has...it's brutal.
I've abandoned most of the "built-in" PvP and gone solely to fight clubs on my high Soul Memory characters. Kinda sad, seeing as the PvP in this game is much better than DkS1 (and leagues better than the SPS PvP of DeS), but much more of a pain in the ass to make the most of.