Ok - a few things to clear up.
The gradient is important to consider in the one-engine inoperative case - it doesn't matter if you're IMC or visual - the only difference is, if you're visual and you're not achieving the minimum gradient to avoid the ground, you'll get a great view of the it before you smack into it...
Type A charts are usually provided by the airport authority and cost a fair bit to a) produce and b) purchase. They identify ALL obstacles in the splay (based off the centreline, usually, but sometimes in special cases they do offset calcs such as at YSCB RWY 35) which is a straight line extending out to 15,000m with a 15 degree "splay" either side. The benefit of a Type A chart over the basic RDS info is that you can identify the most limiting obstacle and hence the most limiting gradient. Pretty sure the splay is based off 35' from the DER - haven't looked for a while and don't have my docs with me...
Anyway, with the above data, you can calculate less restrictive engine out climb gradient requirements...