Just a reminder, too many of you are using terminology inexactly, that could confuse someone not familiar with the systems.
The intensity of the leeches (in imbuing terms) does NOT go down from adding SSI. The DISPLAYED EFFECTIVE VALUE is what goes down (or up), based on the overall speed of the weapon.
There is a sliding scale for the displayed effective value. The same amount that might be 50% on a middle speed weapon may be 40% or less on a fast weapon with SSI added, or showing the cap of 100% on a slow weapon. All would have the exact same base percentage in terms of imbued value.
This sliding scale for HML & HLL based on weapon speed was added a year or two into Mondain's Legacy. Prior to then, leeches worked differently than now, and the Soul Seeker minor artifact from paragons (for example) had the same displayed (and actual) intensity for all 3 leeched.
After the change, they remained the same non-displayed INTENSITY, but the displayed effective value of two of the leeches dropped in relation to HSL because of the base weapon's speed combined with its 60% SSI.
To this day, many of us consider that this was a bad idea, simply because of the confusion that occurs as a result of Imbuing SSI with leeches, and the resulting displayed value changes. And, that's before the bugs that resulted in Leech values getting screwed up on weapons from other SSI sources.