I've had a good chance to play as Bebop a lot and can confirm he is always going to be viable from early game to late game. Here's what (You) need to do in order to succeed as him:
>Early game
<Put points in hook and the hammer arm first, then equal everything out from there
>Your laser regular attack got nerfed recently, making the ranger much smaller, don't worry about putting too much points in your regular attack since that's not where the majority of your utility comes from
>At most, you should only need two items in the bullets category: The one which restores your health, and the close combat one. These fall off quickly so make your use of it in the laning stage
<Buy Mystic Reach and Mystic Burst first then get the boots and the T2 boots afterwards
<Get Mystic vulnerability next
<Early game in the laning stage, your best way to get kills is to bait enemies to get close to the guardian, hook them, then if they aren't already near the guardian (to take increased damage), use your Z/Arm skill to knock them closer to the guardian, taking even further damage
<If you have a surplus of spirit points, get Hook max leveled out for the faster cooldown, this makes a big difference in starting teamfights and picking off priority enemies
<Your main purpose as Bebop is to single out enemies who are huddled together with their teammates and pick them off
<If grabbing them isnt enough and they escape, or the rest of their team comes in to back them up, use your ultimate from a safe distance but with good enough coverage of the fighting area to deal insane damage at a really far distance
<Mid game, go for Knockdown first which will help you land your hooks better as well as pick off enemies that you managed to hook successfully
<Next item of import is the extended reach one, imbue it on your hook skill and you can grab people halfway across the map if you land properly
<If you have extra money after that, go for bullet armor/spirit armor depending on who you're facing. Get the advanced tiers of bullet and spirit armor if you face a pain in the ass haze or seven, respectively
>Your worst enemy as Bebop is McGinnis as her spirit wall can totally fuck up your ultimate if you have already started using it. You may also have difficulty facing Lash as his ultimate can stun you and take you out of your own ultimate, he also has really good escape options which make it hard to pin him down or kill him
>Your best enemies as Bebop is basically everyone else. You may be mostly stationary in your ultimate but you have good enough range to pick off flying Vendettas, Grey Talons, and Sevens who have knocked their ults off
<Mid to late game, your MUST-HAVE item is Diviner's Kevlar for the armor and the lifesteal
<Your ultimate has lifesteal built in on its final level but that may not kick in soon enough. After buying Knockdown, you might want to prioritize getting Diviner's Kevlar next
<The sky is the limit after the lifesteal. Go for Escalating Exposure and Mystic Reverb next for added damage, lifesteal, and slow, making your ultimate an extreme wombo combo of death
<If you have extra money, go for the green upgrade which grants a shortened death cooldown and leech
By mid game, following this guide, you should be at the point where your ultimate grants you extreme lifesteal, enough to solo most enemies without stuns and even Hazes using their ultimates will be like putty against your laser beam which bypasses her evasion. I've even faced off Abrams, Warden, and Yamato at the same time and survived because my beam was dealing more damage and granting more healing than they could output in damage. This on its own is enough to earn your keep on any team as bebop but you also have the hook which makes you invaluable in breaking the ice at chokepoints and making your path to victory easier.
I fully expect them to nerf his beam later, but for now, he seems to be a mainly hidden gem among Deadlock players and people rarely attempt to queue as him. If you can find a team with Lash, Dynamo, and Wraith, you'll be nearly unstoppable.