Elf: I could be crazy, but I don't recall having tons of Heart Scales in Gen4? Even if they were everywhere and plentiful, the 4 move limit is a pretty big deal in Pokemon, and you won't always have the right set of 4 moves. Vs. random monsters & gym mooks, you won't know exactly what you're facing. Vs. gym trainers & "bosses", sure, I guess there's "lose once, modify your loadout," but there's also competitive PvP, which won't let you see your opponents set-up in advance. So vs. randoms and PVP, you can't necessarily set the perfect setup, and vs. bosses it still requires losing once which eats cash to know it. (or checking the Internet, sure.) This makes me inclined to lock DL Pokemon to a single 4 move set, yes.
That said, I'd be willing to consider that Gen4 Starmie should really have a different 4 moveset, since holy crap, assuming 1 Hydro Pump misses, the stat topic set gives him just 2 PCHP damage to win with pre-Struggle, which gets him owned by any sort of crappy healing at all (loses to ROBERT?!). Also, not sure that even if Gen4 Starmie's best set is considered to swap in Bubble Beam over Confusion will help... a full loadout of Bubble Beams all hitting is ~5.4 PCHP, 4x Hydro Pumps are 2 PCHP, Estelle can heal up 14 times ~= 14 PCHP worth of healing, which will be somewhat inefficient due to having to heal early, but probably not THAT inefficient. And Gen4 Struggle is really bad in its self-damage so even if Estelle only barely out-heals, she should still outlast. She might even win pre-Struggle if Freeze off her physical deals enough damage, as the 10% HP loss effect presumably ignores 6x Cosmic Power, and she can sit on a 200 CP Barrage to force early heals out of Starmie. (This is a lot closer though, and now that I think about, I'd be inclined to agree that Starmie would be better off focusing on buff / heal backed by Bubble Beam and just skip the confuse game entirely.)
(Obviously, this all might be moot for Gen1 Starmie! Dunno.)
