So as the clock ticks down to the inevitable rotation, I'm gonna share my 84% win-rate Final Boros Deck Wins list:
Creatures (18)
4 x
Dauntless Bodyguard4 x
Skymarcher Aspirant2 x
Kari Zev, Skyship Raider4 x
Relentless Raptor4 x
Benalish MarshalPumps (8)
4 x
Pride of Conquerors4 x
Heroic ReinforcementsAuras (4)
4 x
Cartouche of SolidarityTokens/Ramp (3)
3 x
Legion's Landing4 x
History of BenaliaRemoval (1)
1 x
Baffling EndLand (22)
3 x
Aether Hub4 x
Clifftop Retreat4 x
Inspiring Vantage10 x
Plains1 x
Shefet DunesYou wouldn't believe how fast the deck hits the city's blessing. Opponents usually just don't know where to point their removal, because the deck goes wide and tall at the same time. Games usually don't go over T6, so it is literally a 5 minute match deck.
Enjoy it while you can!
As for rotation, well except for the lands and kari zev, the cartouche is actually the biggest hit. The cartouche does 3 things, first it adds 2 permanents to the board for the blessing, let's you do 1 extra "hasty" damage early and let's you attack into any potential blocker opponent drops thanks to first strike. You just don't have a replacement for that in GoR. Demotion is an option at the same cc, but you don't do extra damage and only add 1 permanent to the board.
Other cards that look good to include are Legion Warboss, although the 3-slot is already packed with very strong cards (benalia and the marshals). Aurelia at the top end as a 1 or 2-of, but you'd have to cut the reinforcements. Chance for glory may actually work as a surprise card, but is very situational and narrow (but often 1 or 2 more points of damage is really all you need). Tajic could work too, but has the same issue as warboss. Vindicators look a little too slow and most of the other playable mentors won't be doing much as most of the team already has 2 power (although it could be interesting to add snubhorn sentries with the mentor cards).