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it also depend what else you do in a week exercise wise
I agree - if nothing else, it stops running being boring.
Injury-wise, it's proving to be a niggle more than anything else, and I'm working on technique to mitigate any further problems.
NotThamesWater-
I'd be careful with increasing quantity and having too much quality in there. I don't think you need any more than 1 x interval and 1 x threshold/tempo session for quality, then everything else easy pace including the long run. McMillan's generally pretty good with recommended paces in my experience, although I'd err towards the slower end of the easy run paces. So easy/long runs shouldn't really be anywhere near HM pace. I'm normally running easy runs about marathon pace + 60/90 seconds.
I think you can go a long way simply by increasing mileage, assuming you've got the time and patience for it. Even if you're targeting 5k, which is still predominantly aerobic.
PhilPub
Agree about the quality of the quality sessions, it also depend what else you do in a week exercise wise, you can remove quite a bit of the burden of long runs with bike sessions and could remove some of the strength work by adding in core strength sessions as if I recall correctly you suffered some injuries last time you ramped up your training.