@Lynora
25 attempts @ 20 energy each (for a hard node) yields 25 *0.4 = 10, so you're doing fine.
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Separately, for anyone collating the data from this thread, I just made 49 more attempts and got 10 more shards. Rate = 0.02041 per energy spent
was 18/78 (these first 78 attempts were reported in a previous comment, so don't double count them!)
Current status: 28/ 127 (all attempts on 10-energy node, Fleet 2-E, normal) Rate = 0.02205 per energy spent
Regressing to the mean after that great 0.024 per energy start. More evidence of 0.02 per energy drop rate.