I found alien rulers really boring, and liked the robots except for the bit where they’re too expensive to use. Some of the robot abilities create neat opportunities–Overcharge allows you to finish off a bunch of low health enemies and–when upgraded–lets you smash through obstacles to create new pathways or get the jump on enemies. Other abilities let you use the robots as mobile cover or as a dedicated armor-reducer. I got a lot of use out of the free robot and any that I DID manage to build, but I found it was rarely the most pressing use of funds so I didn’t get to have as much fun with them as I would have liked. Combining the robot squadies with WOTC means you can spend XCOM Ability Points to fill out more of their upgrade tree. A robot with all possible upgrades instead of just the standard one per level is on par with any of the tricked out Colonels I managed to produce if not on the same level as a fully upgraded Reaper or Templar.
In one particularly memorable fight, I rushed into an enclosed compound to rescue a civilian who turned out to be a Faceless. The soldier I sent didn’t have the health to tank a hit and no one could get into position to take a shot. But I was able to Overdrive my robot, and send them crashing through the wall. They were able to get a shot off and open up a shot for my other units and I was able to save the unfortunate soul. (Who then went on to trigger ANOTHER Faceless all on their lonesome, but I was able to sprint a Ranger close enough to deal with the problem without any fancy moves :D). It’s not the only situation where the robots opened up new possibilities for me and gave me interesting tactics to consider or simply saved someone’s ass.
The Alien Rulers make for some really tense and interesting encounters if you’re lucky. But they can also produce some of the most tedious–or if you’re well equipped–most boring sequences I’ve encountered in the game. Their massive health bars and interrupt abilities mean that you can’t deal with them very effectively in a wide array of circumstances, but that you’ll still nonetheless defeat them after they run away enough times to only have a little health left. The alien weapons are neat, but they’re nowhere near as powerful as the Chosen weapons if you get WOTC and are only marginally more powerful than the standard kit; I didn’t find them terribly worth the resource expenditure and they certainly didn’t help a lot against the rulers.
The one thing I really liked about the Alien Rulers DLC was the armor you get from defeating the rulers. They look absolutely ridiculous in the best way and they have not just powerful abilities, but fun ones.