At level 1 with a D-blade, you're going to be healing for just under 6 (5 base, 0.8 scaling) hp on each proc.
At level 6 with a D-blade and BF sword, you're going to be healing for just under 23 (18 base, 4.8 scaling) health on each proc.
At level 11 with a D-blade, IE, and some Zeal item (which doesn't matter), you'll be healing for just under 38 (31 base, 7.8 scaling).
At level 18 with IE, BT, Dominik's, Scimitar, Elixir, a Zeal item and boots, you'll be healing for just under 80 (50 base, 29.5 scaling).
The heal is utterly insignificant in early laning. By the time it gets to a value large enough to matter at all, you're at a point in the game where you don't need that healing.