Correct me if I'm wrong, but isn't a common complaint of the Blue Sentinels that you get little to no action before hitting NG+ and beyond? Assuming you do get summoned to aid someone, hosts will typically get murdered before you finish loading in since you get summoned after the Red has already landed and has begun the hunt for his victim. So how does Way of the Blue actually end up helping, exactly?
Giant Seeds are also pretty laughable. How many did you use on your first play through? How many were you aware of existing in the first place? Even if you are aware of what they are, what they do, and how to get them, you must know that they aren't guaranteed to be there when you need them. Hell, even assuming you have one on you and know how/when to use it, your hypothetical ganker wouldn't be annoyed by it much at all. If Soul Memory weren't a thing, it'd be a pretty damned good bet that your invader has enough gear and know-how to one-shot anything that attacked him anyway, since he wouldn't be invading an area where the host had half a chance of defending himself. He's a troll, not a PvP player.
How many effigies did you burn your first time through? I burned zero, because they were a precious and finite resource. Also, they act the same as cutting your ethernet cord, so it's not really a solution to the problem, is it? If the problem that Soul Memory is supposed to solve is evening the playing field for newbies, cutting them off from interacting with their fellow Souls players in any meaningful way is kind of a silly thing to suggest.
Don't kid yourself into thinking that Soul Memory is to ensure that you find a fair match-up for PvP. It's to ensure that a new player doesn't get totally wrecked by weapons and spells that they haven't gotten a chance to get for themselves within their first few hours of playing. Soul Memory ensures that both you and your would-be victim have had access to roughly the same amount of the game. It impacts the earliest chunks of the game more than it does the latter portions. That's the point.
TLDR: Soul Memory wasn't designed for you. It was designed to shield newbs from trolls and horribly one-sided invasions. It works well for doing just that.