None of them can move through hills and forests with 3 moves, attack @ 60 strength, twice, in a turn. Getting promotions on Warakus is easy with the recon card. Also, there's nothing stopping you from getting a GG and a Waraku, too.
Also, your claims are false. You get the Waraku with machinery, and the unit can be upgraded from scouts. Leveling it on a city state is easy. You'll have several of them @ level 3 before you get out your first Hwacha (which requires gunpowder and has to be hard built).
The mistake that people make is they send them into AI controlled city walls and Xbows before they're leveled. That's dumb. The correct decision is to level them on something weak (AI that sends its units at you outside of their cities) or on a city state. Then once you get several of them to level 3, they wipe everything off the map.
Even better: build 2 scouts and get them to level 1 scouting and fighting barbs. By the time Machinery hits, you can have two level 1 Warakus depending on how much gold you saved, which you can quickly level to 3 within a dozen turns by fighting a city state. Keep the city state alive for more "leveling sessions with Warakus" (16 exp/turn). Or use free cities (works just as well). All of this comes in much earlier then anything else you've mentioned. You can be running a dozen of these fast moving, double shot Hwachas by Renaissance.
EDIT: What people miss about this unit is the synergy of its double shot with the 2x experience recon card. This means Wakas level 4 TIMES AS FAST as any other unit in the game.
