You need to read the job descriptions carefully as every company slices these things differently. Different shops mix terms up different ways. That said (IME):
- NOC: Network Operations Center: Concerned primarily with networking operations, focused on route/switch/wlan, with security as a secondary function.
- SOC: Security Operations Center: Concerned primarily with security operations.
It frankly sounds like you're looking at one firm for your definition of tier 1, 2 & 3. More generally, tiers look something like (IME):
- First line analysts: initial data collection, triage of data, determine what to elevate for more detailed analysis.
- Experienced analysts: deep dives on particular findings, followup with more sophisticated techniques, often generating final customer deliverables.
- Elite analysts: custom pentests based on client specific requirements, R&D and next gen techniques.
For a pen test firm, most Tier 1 functions are pretty automated, or they're loosing money. So I wouldn't expect a tier 1 at a mature, successful pentest firm to be doing more than a modest amount of ad hoc programming work; they've got a well practiced playbook and toolset that they'll be following. Tier 2 folks will be expected to be able to ad lib at will, so if that's your goal, that's where you want to be.