Jonny Razor: This is a close combat fighter, don't waste time making ranged attacks with him!
Glen: You mean Gaen? This is a mediocre ranged fighter (with 2 wounds), keep her away from close combat!
Vander: You mean Vunder? This is a close combat fighter, don't waste time making ranged attacks with him!
Gor: You mean Cor? This is a short-range fighter, keep him away from close combat!
These are poor hive scum, don't understand why you expect space marines! They have relatively low cost compared to other fighters you can hire. These are not cripples, they have some exaggerated strengths and weaknesses compared to your bog standard average fighter (cawdor/chaos ganger stats). Why someone would pay for them? It is general consensus that any hired gun (regardless of hive scum, bounty hunter or strength/power) are all overpriced and not worth the credits. Maybe some situations allow you to hired them for free, in which case they are worth it from a narrative perspective, and that they're better than nothing, and they all serve some niche usage.
If you need to hire fighters with good WS and BS, check out Baertrum Arturos III, Yolanda Skorn, Kal Jericho, Slate Merdena, Vorgen Mortz and Vandoth.
As mentioned, we already have a bunch of special characters with good stats (WS & BS 2+ or 3+). GW wants to make a bunch of these characters, so if all of them have same type of good stats, they all become very similar or even identical. This is already the case for close combat weapons, where they added so much, many of them are identical (with different names) or same name (with different stats). So in order to make new unique characters, they must make WS and BS unbalanced, the result is several of the characters you mention. This is not easy to understand if you just read a single book with 10-15 characters. But if you get a fan compilation, you would see the multitude of characters we already got:
- Hangers-on: 23
- Standard: 9
- Outlaw: 5
- Brutes: 9
- Pets: 13
- Alliance: 31
- Hive scum: 14
- Bounty Hunters: 28
More than 100 fighter profiles for fighters outside your 'core' gang (leader, champs, gangers, juves). They can't all be BS and WS 3+! They need unique differences in characteristics, or they don't have any purpose.