Rexler Brath was in the very first squad I ever took to a tournament, which was the very first game of X-wing I had played against another person. He was also in the squad I won acrylic templates with at the Regional level, and has been a part of both squads that I've used to earn Regionals dice. My first ever Gencon, I went 5-1 in Swiss with a Rexler Brath squad.
So of course I had to start 2.0 with squads trying out Rexler Brath. My experiences are limited, but I've found him to be an interesting and rewarding ship to use so far.
His role in 1.0 was interesting. He was the more expensive, higher PS Defender with a very narrow pilot ability. Generally, when he worked, it was because that extra PS allowed what was essentially a heavy jouster to act just a bit like an ace.
2.0 sees a radical rework in both the pilot and the ship he flies. The Defender gains a shield, boost, evade, sensor slot, and a better dial. It retains its other stats, its white K-turn, missiles and cannons, and the extra Evade action from moving fast. It loses access to Modifications, TIE/D double tapping, and costs a healthy pile of points. Rexler Brath the pilot sits at I5, which seems a bit better than his old PS8 due to the rarity of I6 and has a much easier to use ability than his old version.
The effects on the game table are that he costs more like a TIE/D, but punches more like a TIE/x7, sort of. The biggest gains to the chassis were in maneuverability and defense. Gone are the regular 4 hits from an Predator empowered HLC or the control/damage combo of Ion Cannon/Primary double tap. On paper it makes for a tougher ship, but a ship that pays a lot for its toughness. My initial concern from when it was first spoiled is if it could do enough damage for its cost.
Fortunately, unlike the x7, or 2.0 Defender still has access to Secondary Weapons. This, I have found, makes a big difference. As of August 2018, your 84 point Rexler Brath can add just a few points to get some supplemental weaponry. 3 points gets you Homing Missiles, and 4 points give you an HLC. 4 more points give you Juke. These all interact interact with Rexler Brath in interesting ways.
Homing Missiles encourage you to grab an early Lock, and in all likelihood let you keep it for a turn. Most opposition won't want to give you 4 dice (that ignore the defensive range bonus) with Juke, so they'll accept the single damage. Because of Rexler's ability, however, that damage can get flipped up if you have an Evade. So unshielded targets still get punished while Rexler retains the lock for the next turn's closer range shot.
The HLC has further interactions. So far, I haven't played to maximize the bullseye. I have found, however, that it happens more than a few times a game, especially against swarms or large based ships. Even when ships moving after Rexler can barrel roll or boost to dodge the bullseye, that can help trigger Juke because they're now an action down. Rexler's ability can still kick in on the HLC as well, so the cannon that doesn't crit can crit when it's fired by Rexler Brath.
All these things provide options. You have 4 dice to throw at Range 1 and in the Bullseye. You have an easy damage against high defense targets if they're not in the 4 dice zones, and you have a frequently Juking 3 dice attack that threatens crits at all other ranges. Selecting maneuvers to maximize the weapon you want for the situation you're dealing with is a lot of fun and makes for interesting decisions. Instead of overwhelming firepower or just being tough, you get an incredibly tough ship with flexible firepower options that allow you to adapt to a wide variety of situations.
On top of all that, Rexler's I5 gives him the edge over any generics and quite a few named pilots. It puts him on equal footing with some premeir ships, while his missiles and white K-turn can keep him competitive against I6 stuff. He retains his old jouster/ace hybrid status.
I've purposefully avoided talking about the right sensor slot. Advanced Sensors, FCS, and Colission Detector all are strong, and all change the ship in their own way. Personally, I find myself relying too much on Advanced Sensors when I've had it equipped, but I expect others don't have that problem. I feel like I make better long term tactical decisions when I don't have AS, and FCS, being cheaper, allows for a bigger bid or better stuff to accompany the Defender. Long story short, I don't think I have a clear view of the sensor options, and don't really trust my own opinion.
Anyway, it's way too early to pretend any of these observations are definitive, I just thought I'd share what I've seen so far for those that are fans of the TIE Defender.