Please Stop Overtuning Events
Shield Generator bug aside, the Jar Jar event is a joyless slog to do at R5. Tier 4 in particular has almost no strategy involved but requires you to slowly tickle Darth Maul to death over 10 minutes...
Forum Discussion
They want it to be extra tough at R5 so that you'll expend resources and/or buy them to get your gungans to R7, R8, R9. (Same as why the naboo raid has a Tier 7. So you'll take all those units to R9.)
While I'm surprised that datacron requirements were reduced to R1, 3, and 5, that doesn't discount that CG keeps pressuring players to R9 their whole roster because even R7 is meaningless in some events. (without even mentioning ROTE TB where R9s get wiped with one basic attack.)
