As an user and abuser of Cress in the present and the past, I can definitely say the novelty has worn off quite a bit. I often found myself being set up on, or phazed, and Cresselia often became a Pokemon that I sacked to get another teammate in safely. Cresselia is actually pretty underwhelming without any boosts, and any support sets are immediately stopped by Taunt. I've opted to switch out Cresselia for Tangrowth, which seems to have been completely forgotten in the current Cresselia craze. Tangrowth still does a magnificent job of walling physical attackers, and Regeneration is super useful for extra recovery and makes it very difficult to kill, even with a super effective physical attack. Once Tangrowth was added to my team, it became leagues more successful as I wasn't bogged down with Cresselia. In all honesty, it was more of a hindrance than a help in most cases. Sure, those few times where I managed to set up to +6 and sweep were quite satisfying, it hardly happened, and when it did, I was usually playing an inept opponent.
However, one of the new additions to RU that I am enjoying immensely is Aerodactyl. Aerodactyl almost always manages to get Stealth Rock up with its blazing base 130 Speed, and can Taunt virtually anything as well. Earthquake and Stone Edge are great coverage moves, and do quite a bit of damage even without a Life Orb boost. Aerodactyl makes a great revenge killer to stupid shit like Specs Porygon-Z and Specs Moltres. As for the other additions, I don't really think they are that good in the current metagame. Before the tier shifts, Sigilyph was super hyped up, but from what I've seen, it's been incredibly disappointing and fails to do basically anything in battle. Anything that can hit it hard before it boosts with Cosmic Power absolutely destroys it, and Volt-Turn strategies easily break through. Powerful physical attackers such as Choice Band Durant can destroy Sigilyph even if it manages to pass a burn through Psycho Shift. Whimsicott is little more than an annoyance, and is easily dealt with through the use of virtually any Grass-type, though faster ones such as Sceptile should beware a priority Stun Spore, which is in my opinion the most annoying thing about it.
I'd also like to draw some attention to some rather underrated Pokemon in the RU metagame that have proven to be excellent team members. Samurott in particular, has worked wonders for me, specifically the Swords Dance set. Everyone expects the Special set, and ends up switching in Slowking on a Swords Dance, only to be mauled by Megahorn, which also can OHKO Tangrowth after a boost, a feat no other physical Water-type can boast, even Feraligatr. Access to priority in the form of Aqua Jet just makes it that much better, and allows it to revenge some otherwise troublesome opponents. Feraligatr is in the same boat, though it cannot OHKO Tangrowth with +2 Ice Punch, but it does boast slightly higher Speed, Attack, and overall bulk. I just prefer Samurott for its access to Megahorn which destroys any Grass-type switch-ins as well.
EDIT: FUCK HUSTLE'S INFURIATING ACCURACY