Finished searching all Waterfall places after getting through victory road, so I have done everything possible including picking up all hidden items, fighting all trainers everywhere... and just went into the E4 with this:
--Cybele
Timid, Natural Cure, Roserade 61 @ Black Sludge
-Petal Dance
-Shadow Ball
-Leech Seed
-Toxic
--Kirin
Adamant, Flash Fire, Arcanine 62 @ Shell Bell
-Flare Blitz
-Wild Charge
-Outrage
-Crunch
--Alfven
Bold, Sturdy, Magnezone 61 @ Rocky Helmet
-Thunderbolt
-Flash Cannon
-Tri-Attack
-Metal Sound
--Nereid
Sassy, Water Absorb, Lapras 62 @ Leftovers
-Waterfall
-Ice Beam
-Psychic
-Drill Run
--Ankohl
Calm, Levitate, Claydol 61 @ Rocky Helmet
-Earth Power
-Psyshock
-Ancientpower
-Signal Beam
The E4 are just about these levels in Challenge mode lol.