The actual Illushyn Sturmovik had significant as an attack and anti tank aircraft. The heavy armour protection reduced its war load and of necessity forced it to perform relatively light attacks thereby forcing multiple sorties. Furthermore the armour while providing wide coverage could be penetrated with armour piercing 20mm rounds and when it was the penetrating round and its fragments would bounce around inside the steal armour causing havoc and perhaps killing the pilot. the Ju 87 had a more 'all or nothing' armour around the pilot that either protected him fully or allowed the round to pass through.
The Fairey Battle modified as a ground attack aircraft might have a pair of long battelled Hispano guns and perhaps about 300 or so pounds of armour added. The prone bomb aimer might need some armour. With an improved bombsight such as the Mk XIV it would be possible to roll bombs into armoured targets.