Su-30/Su-35 don't have external fuel tank capacity under the wings, so don't search for them. Su-34 have a lot of range without fuel tanks... like other flankers but have the capacity to carry them under wings. Still, fuel tanks are more or less ripped open on high G manoeuver, so jet carrying them have big restriction, way better to be clean and be able to do SAM evading.yes but that is expected. what was not expected was so many attack chopper/Su-25 in the battlefield from Belarus in North to Crimea in South. when you look at pics of Su-30/Su-34/Su-35 they rarely carry any external fuel tanks and lightly loaded relative to there total payload. while Su-25/Attack chopper carry external fuel tanks most of time and are more loaded to there limit. they are carrying more the weight burden.
this video of 2014 from Crimea. that gives idea how long they are preparing for this kind of approach.