Have a look at FCOM 3.05.35: config 3-one engine inop
For the A320 the MLW of 66.0 is less than the app. climb limit until a 10,000' elevation strip which is higher than allowed anyway. The blank sections of the table may be outside the ISA plus limits(???)
In the overweight landing situation you may elect to use the config 2 figures which show 76.8 tonnes at 44 deg and 2000'. In an emerg. reland you are unlikely to consider this anyway.
Also the QRH gives direction 2.25 (two eng.) or 2.50 (one eng.) regarding using a Config 3 landing (thus Config 2 go around) to improve performance in the overweight situation. Although this is not directly associated with the approach climb issues.
The A321 is a LOT more limiting than the 320.
Hope this helps
