NGL it is way harder to be a SR. CL4 in Research, GSD, and Medical compared to other departments.

the best solution to being 'stuck in a department' is to expand outwards rather than upwards, speaking from personal experience, i haven't held nearly any senior cl4 roles (other than o1 major ages ago) prior to site admin, but have fairly valuable experience as i've tried a wide range of roles on the server.

while combat or non combat isnt everyone's favorite, it can still be great to try out different departments and maybe even get cl4 in it, a wide range of experience across multiple sectors will always be more valuable than extensive experience in one department.
 
But why do DEA have 5 SR. CL4 They really don't like compared to medical which actively do RP and can change many things on site. This is also a progression thing cause I am just stuck at the minute and getting a SR.CL4 is going to take another 3-4 months on top of my 6 continuous months on the server ( not counting my time before these 6 months). I find it dumb people who have less experince and time on the server can easily get a SR.CL4 while I'm stuck as a Consultant cause there is one spot that opened in easily over 7 months and I couldn't get it.
I m not entirely sure but I’m pretty sure it’s because it’s a combative department and requires a bridge between special agents and Directors considering having only 2 people lead jr cl4s with the role DEA needs to have on surface would become difficult for the directors so managers should just be to bridge that same with ISD