The thing that the Ex-Bee can do is pretend to be a Executioner and that'd be easier in a large double-blind game where deceptive Mech movement, and limited information are it's friend, such as bait-and-switch between the two types of Executioners, that's if the Executioner can get out of sensor range and the Ex-Bee can be positioned in a realistic place so the opponent doesn't twig right away, Executioner Prime goes into a confined mobility space (i.e a city), loses it's followers target lock, swaps places with an Ex-Bee Prime, surprise UAC20 and an opponent that wont follow for Executioner anymore. The mech has uses just not so much in a standard pick up game and that's fine and as much as BT isn't realistic, it adds some realism that not everything is designed for two map sheets and a hand full of turns, because that would be dull.
Honestly its not even good at that. The standard Executioner (B Config) offers similar usable firepower in a confined mobility space, like the city environment. It is way more usable in an urban / restricted mobility space due to its increased movement and jump jet range.
Looking at it the Executioner B-Prime can throw this down range and maintain heat neutral (without movement)
2 Large Pulse = 20 Damage
1 UAC 20 = 40 Potential Damage
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60 Total Damage (Potential) without overheating
Or swap out one of the LPLs for an ERPPC and throw 65 points for a +5. Adding in the UAC/2s even if all shots land only add in a whopping 8 points to your full alpha... and say goodbye to your heat scale.
The Standard Executioner ( B Config) can throw the following down range
and jump 4 / run and maintain heat neutral:
1 UAC 20 = 40 Potential Damage
1 ERPPC = 15 Damage
1 ERMlaser = 7 Damage
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Total: 62 Damage (Potential) without overheating
This version also has an AMS to defend against missiles and about the same rough damage output (while maintaining heat neutrality) as the Executioner B-Prime, all the while being able to run (or jump) circles around it. Also the armor difference is a staggering half a ton.
The Standard Executioner (C Config) can throw the following (while doing whatever movement it wants and bathing in inferno jelly or running with engine hits...):
1 UAC 20 = 40 Potential Damage
1 LRM 20 = 20 Potential Damage
1 ER Small = 5 Damage
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65 Damage (Potential)
Keep in mind the LRMS have artemis and that UAC/20 is Tarcomped so your odds of hitting with those 40 point double taps is insanely increased.
In every single scenario I'd rather take the Executioner over the B.
I'm not sure why people are surprised that the flawed predecessor of the Gladiator Omnimech is flawed.
Not surprised, it makes sense canonically, just pointing out that I don't see any use for it personally. It loses the flavor of the Executioner, and gains nothing over its counterparts. But by all means its not an unwelcome addition to the game and if you like it go for it!