The "cap" rolled for by the runic is still 2%-50% - BUT....
That 50% is not displayed, but is now multiplied by a number, based on the weapon speed (and SSI does affect it), and in turn that number is capped at 100% (50% for archery weapons, last I heard).
The Life Leech and Mana Leech properties now trigger every hit, instead of the 2%-50%.
What they return to the wielder is a number of Health/mana (depending on the leech type, based on the following:
(1% to the modified leech amount, determined randomly) * (the old amount the leech property would return: 30% for Life leech, 40% for mana leech) = amount leeched.
So, if an item has Hit Life Leech 72%,
(1% to 72%) * 30% = 0.3% to 21.6% of the damage done, on each hit, rolled randomly each hit.
So, if you're hitting with it (on average) for 100 points of damage, you will get back 0 to 22 points of health every hit - probably averaging about 10 points if the Random number generator is nice to you.
A person using the very fast "Soul Seeker" (30% life leech; the equivalent of the old 40% ability/80% intensity, at its weapon speed), hitting for 100 points on average would get -
0.3 to 9 Health back per hit - but will hit a LOT more over time due to weapon speed.
At the same time, it will also be leeching 0.4 to 12 mana back per hit (40% of 1 to 30%)
And have a 40% chance of leeching 100% of the hit amount as stamina.