Airbus757
On the airbus these figures are presented on three charts. For a missed approach we select TOGA, gear up, and move flaps up one step to conf 3, conf 2, or conf 1+F. From their respective charts we can see the expected climb gradient and as long as it is equal to or greater than the required gradient all is good. This required gradient is listed on lido charts. It is 2.5% or a non standard requirement. Also if a turn is required we must allow for 0.9%. We maintain that configuration until the missed approach altitude is reached where we level off and clean up to hold or enroute speeds.
Yes, it is possible for a pilot to make a few spot checks of expected climb gradients in various configurations and compare them to the overall gradient required by a Missed Approach.
But doing so is not the same as a full performance analysis computed by the professional engineering entities.
As you are no doubt aware, airplanes do NOT climb along linear paths -- aka "gradients".
During climb (all engines or OEI) thrust is decaying, time limits for power settings are reached, acceleration segments are required for cleanup, etc.
Our actual climb paths are anything BUT "gradients".