Since Robyrt has generally summed up the tiers for 1player and tournament mode (and I mostly agree with those), just figured I'd take a try on 2-Player/Multi-Player.
The top, because the thing they do best, is good enough to counter or shut down most other bots.
Still rules the air, and most HAR's (and players) have trouble/difficulties attacking without jumping. An average player in a Gargoyle that figure out how to lock down enemies jumping, can beat a better player in another HAR.
The defense specialist, Rising Blade is just that good. Basically can negate, cancel, or just counter almost any kind of attack the opponent tries at you as long as you can read it and time a Rising Blade perfectly. All over good bot otherwise, but that one move takes it to the top.
These have the tools to fight against any opponent, but lack that little extra of Tier1.
Difficult bot to do well with, but it is surprisingly one of the hardest hitting bots in the game, and can pull some amazing combos out of nowhere. It's special moves can be vulnerable and feel quirky, but as long as you can make use of them to feel unpredictable to the enemy, and setup a surprise combo, it can finish a game near instantly.
Fast, versatile, defensive. There are few things you can't defend against as an Electra, and you have several high priority and/or damaging attacks.
Generally considered the best combo bot, and very aggressive. It is also one of the few bots that has a good way to approach to attack without jump attacks, with the very useful flip-kick. It does have its weaknesses, particularly it's short reach, and if you can counter it, it falls together very quickly.
This would basically be the average ones, they have tools for most things, but doesn't really stand out.
The strengths: Easy to learn, solid all-rounder, good specials. The weaknesses: Everyone knows it, easy to predict, generally poor basic attacks. To be blunt the jaguar is one of the better bots to beat up new and/or unskilled players with, it's possibly the worst bot you can use against a good/experienced player.
Personally I find jaguars to be almost as easy to beat as Shadows.
Most would probably rate this one tier below, but the more I play with it, I really struggle to find weaknesses. Good: standard attacks, reach, priority/pokes, damage and endurance, can trade hits with anything. The bad: Ranged attacks, big hit-box. The bot basically plays like a master of all the basics, and most of the specials are traps. EarthQuakeSmash also lets you deal with turtling/blocking, and is an excellent way to force opponents to move/act.
This tier is where bots start having severe flaws that can make certain match-ups incredibly difficult, if not impossible vs similar skilled opponent.
Difficult to play with or against. Unfortunately it lacks ways to deal with some problems. Can really struggle against bots that can shut down its jumps, and its jumping is so low it suffers against anything that can spam ranged attacks. Which sums up to suffering against the top half of the bots.
Tremendous damage and some easy and nasty combos, but can be very hard to land them. It also has a weird hitbox that often feels easier to hit than many other bots. Jet Swoop is an alternative way to approach/attack, but doesn't give enough variety in approaches to be able to get through a good block. Suffers against anything that can punish its air-game or has good defenses.
Thorn has one fantastic special move Speed-Kick, good reach, and a really good poke. And almost everything else suffers. The entire bot lives or dies on Speed-Kick and short but strong combos delivered around that. Using pokes and Speed-Kick for defense. It become a one trick pony, and if someone can negate the Speed-Kick you truly have nothing else to fall back on. Every bot can beat a Thorn simply by learning the timing of Speed-Kick, and find a way to counter/punish it.
The Shadow tier, this is where the poor Shadow is placed because it unfortunately just doesn't work as it should. This is the place for bots that just doesn't work as they where designed, and honestly needs its entire moveset/specials changed and/or re-designed in order to be viable.
Poor Shadow, despite looking so cool, it sucks. Except for a couple of good basic moves like the sweep, the rest are pretty bad, and the special attacks are either too slow or too awkward to really be effective. It's one possible strategy is to abuse sweep, shadow kick, and stun the enemy and abuse the stun lock mechanic with Shadow Grab.
Just a quick note on pilots (you can find more details on the pilot2 page if interested). Not all stat combinations are equal, some characters just work better than others.
Agility under 4-5 is crippling. Low endurance is similarly crippling, and you'd want it at least around the 8. Ironically Power isn't as crippling as you'd think, and you can go decently low on power and still do a lot of damage due to combos.
This means that the three weakest pilots are Shirro, Ibrahim and Milano. Cossette and Steffan are only a single point difference (power/agility) and I consider them to be identical. Angel and Jean Paul are essentially identical for all practical effects, and mostly up to preference.