I was just looking at a crossbow I made with one a few months back...
46DI
40SSI
22HCI
21 Mana leech (Are you serious?)
I mean why do they make things with such LOW intensity? It's just kinda stupid.
Actually ...
21 Mana leech is about right. Mana leech & life leech now take into account the Speed of the weapon. The higher the speed the lower possible leech. This is why you only see 100% hit mana / life leech on really slow weapons (Halberds etc) with no ssi etc... I know that when they made the original change to these leeches my Composite bow with 42 mana leech & 35% ssi became 23% mana leech...
Anway... also realize that for any archer weapon it will leech 1/2 as much as a melee counterpart with the same percentage leech...
Maximum amount possible to leech is 40% of dmg done.
What the "mana leech number" on your weapon is that EVERY HIT it leeches between 1 & "that mana leech #" of the maxium (line above)...
Example.. I do 100 dmg to a monster. My bow Has 30% Hit mana leech...
Maximum mana I can leech is 40% of 100 = 40 mana
Every hit with my bow I leech a random amount from 0 - 30% of that 40 mana.. so on average I leech 15% of 40 mana = 6 mana. THEN it gets halved because it's a Ranged Archery attack.. making the actual mana leech = 3 mana. If it was a katana instead it would have leeched 6 mana.