Well, I think I'll give my two cents by answering the questions and contributing a bit.
1. Does Scarf Heracross have room for your team? Have I convinced you to try him out?
As a matter of fact, no. Choiced (especially Scarf) Heracross just has too many things forcing him to switch after his first attack. Megahorn? Giratina, Scizor, almsot anything resistant. Close Combat? Giratina(-O), any ghost-type, Mew set-up bait, Mewtwo. Stone Edge? Groudon, any steel-type except Scizor. Night Slash? Almost anything with base 100 def or above that isn't hit super-effective. I feel it's better to let him switch attacks. Choice Band works better IMO.
2. What other Heracross sets could be viable in Ubers? There have been talk of MoPCross, pure SD Sweeper, and even Choice Band Heracross being effective. Be sure to share these with us so we can discuss.
Pure Swords Dance sweeper can work a lot of wonders. Simply put:
Heracross @ Life Orb
Guts
Jolly
252 Atk / 252 Spe / 4 SpD
~Swords Dance
~Megahorn
~Close Combat
~Stone Edge / Night Slash
I love this set in Ubers because it has the potential to be very effective. At first sight, this is just the standard Swords Dance set, nothing really special about it. You would be right to an extent, except that there are many things that make this set so special. Swords Dance Heracross is probably one of the most consistent wallbreakers in Ubers.
The gist of the set is simple enough: switch Heracross in on something he can force out and Swords Dance on the switch. With a Swords Dance under his horn, Heracross can OHKO or 2HKO perhaps every wall and tank in Ubers. STAB Megahorn is a must on almost every Heracross set, and in Ubers, it deals with the plethora of Psychic-types that run rampant, easily OHKOing
Lati@s, Deoxys-D, and Wobbuffet. Close Combat is the second attacking move, also being boosted by STAB, it works very well in tandem with Megahorn, killing off Steel-types in Skarmory, Scizor, and Dialga. Stone Edge works well for the last slot, as it handles Flying-types, most notably Ho-Oh and Rayquaza. However, Night Slash is also a decent option, handling Giratina and Giratina-O better than Stone Edge would.
Life Orb is the best item for the set, giving an extra kick to Heracross's
horn, and is mainly used to power up neutral attacks. However, if Heracross is your status absorber, use Lum Berry to get immediate Guts activation, but your sweep will not end early due to Burn or Toxic, or you won't be any slower when switching into Dialga or Groudon's Thunder Waves. As a matter of fact, Life Orb is weaker than a Guts boost, and the lack of recoil is also appealing.
Because Heracross hates fast pokemon, it's best to have teammates to rid him of just that. Choice Band Scizor is a great help for this. A Choice Band Bullet Punch severely dents many Scarf'd and naturally fast threats such as Garchomp and Mewtwo, and U-Turns punch pretty big holes in the walls for Heracross to widen further. Swords Dance Rayquaza is also an excellent partner to Swords Dance Heracross, as his +2 Extremespeed will kill anything that doesn't resist it, and his STAB Dragon Claw easily decimates Giratina, who walls Heracross. Heracross's
wallbreaking capabilities work very well with this, as STAB Close Combat destroys the Steels that resist Rayquaza's Extremespeed, as well as absorbing Will-O-Wisps for Rayquaza (albeit, for his own benefit). Choice Scarf Kyogre is also a nice partner to have. With permanent rain, Heracross's fire weakness is neutered, which is a big help, and Kyogre can hit quick pokemon hard with double STAB Water Spout or Surf.
Heracross can't do too much to make the relations mutual except for taking Grass Knots for Kyogre with great ease. Dialga also appreciates Heracross's wallbreaking, eating up Blissey, Ho-Oh, and Lugia, the most prominent special walls, and in return, Dialga handles Giratina fairly well with STAB Outrage / Draco Meteor / Dragon Pulse.
<3 Wall of text.
3) What are your general opinions about Heracross in Ubers?
Heracross in Ubers is no joke. His key resistances to Dark-, Fighting-, and Ground-type attacks allow him to switch in with relative ease and force a switch. Heracross is also one of the few Bug-types with neutrality to Stealth Rock, making switching him in all the more easier. With excellent dual 120 Base Power STABs that carry great Ubers coverage by themselves along with Guts to absorb Will-O-Wisp and Toxic from the likes of famous walls such as Dialga, Lugia, and Groudon, are attributes almost exclusively blessed upon the brawling bug alone. However, he does have problems with bulk. Being quite a frail fella in the fast-paced Uber metagame where attacks are fired off at every corner, he can't survive very well. His speed is no big help either, being slow even when compared to the omnipresent Base 90 Speed pokemon in Ubers, this doesn't help his sweeper role, nor his problem in bulk. Nonetheless, Heracross is not to be compared to any other pokemon in Ubers. He is arguably the most solid Darkrai check in the entire game as well as one of the best wallbreakers there is to have. Underestimate his abilities, and you most certainly will be sorry.
4) How do you best defend against Heracross?
Most likely, his biggest threat is Giratina. If Spikes aren't down, Giratina can stand up to Heracross and wear him down with Pressure and Dragon Pulses. Basically, Giratina forces a switch on the choice sets and can take on the Swords Dance set head on (lacking Night Slash). The best way to kill Heracross is generally the rule of thumb: Don't get hit before you hit them. That being said, Heracross's frailty basically lets any pokemon over neutral 252 base 90 speed kill him off easily. Priority also rapes him quite hard, which emphasizes Giratina's viability as a counter. The problem is that there are quite a few pokemon who abuse Scarves and their high speed as well as priority, such as Heatran, Mewtwo, and Scizor, respectively. Heracross looks good on paper, but in battle, it's quite a hassle for both the user and the opponent.