Recruitment Process - The recruitment process can be incredibly brutal. There can be long delays in communication before and after screenings and interviews, and the overall process is lengthy as well due to the number of people in various locations involved in every new hire process. They are working on making this process better, but it is still quite painful for many applicants.
Ambiguity - Riot doesn't really do black and white. If you are looking for a data and process driven work environment with people telling you what to do and when to do it, you probably wont fit the majority of roles at Riot. Riot uses data to inform decisions, yes, but context is king. You don't get to lay back and say "well the numbers say x so y is correct". You have to figure out a lot of things, and in some cases this is great ... in other cases, it is a sign of missing direction or leadership and this is something that Riot is beginning to tackle, though it is pretty rare from what I have seen. The result in these rare situations is misalignment, which in turn can cause confusion and frustration.
Blistering Pace - Things are constantly changing and evolving ... some people love this, some people don't. I love it and thrive in an environment that moves at a fast pace, but I know there are a lot of people out there that prefer a more consistently stable and routine work environment. Riot really is a culture of work hard, play hard. If you can't keep up, chances are you will be left behind. To use an anthropological analogy, Riot is hunter friendly, not farmer friendly.
Cost of Living - Dublin, while a super cool city, is incredibly expensive in terms of cost of living. Rents are so expensive that as a sole provider in your family, things can be tight even on an above average salary, especially if you want to live in a family-friendly area around Dublin without a hellish commute to the office. That can add extra pressure if you aren't prepared for this change when moving to Dublin. If you are single and going for an entry level role, chances are you will have to find a flatmate if you want to live close to work.