If anything, that just drove brainless AI3 speedfarming into the contender for 'best coin per second'. You gotta figure; 20% of the time, each individual spin is going to produce an extra 5 electrum -- that's an average of 1 electrum per spin, which means your average AI3 near-mastery is worth 22 electrum instead of 19 now. Considering that you can easily achieve a 95% win rate and you can win a game every 90 seconds with the Shrieker Rush, that's 13.93 EP per minute (vs. 12.08 before the change).
Further considering that the best t50 farmers have a win rate of about 80%, and the stally nature of many FG farmers in the t50 drive the game time average into the 2-minute range, even if you can consistently net a 1-point-shy-of-mastery vs. t50, you're still only getting 12.8 EP per minute even with the new rule.
And with Halfblood's HP and whatnot, it just gets worse from there.
Of course, the value of winning a rare/upgraded card might make t50/HB farming a more valuable activity in some player's eyes, but this little change just totally brought AI3 farming back in my mind.