Hi, simple question.

Will it be hard for me to get groups in high end pve raids (dragon etc) as a shaman with only yellow spec buffs?

When they see your buffs its already too late

Red D/Q isnt needed, but why not got for red S/C?

For high end pve raids most of the shamans have (at least) red str/con buff.
if you go for the yellow one only and put the rest into healing that would also be fine since you are able to healsupport. just dont spec cave for raid-pve. if u plan on a cave spec, just do 1 more dragonraid than planned and keep a full respec.
the outcome of raids/farming ist not depending on a buff although most shamans have rvr-grp-specs and go with that spec on raids.

Well I'm 41 now and can't respec for free

I planned on going cave for the AE yellow dot and I think the instance pbae disease is really viable. I already put 20 points in cave but I guess I will stop there and get red specc buffs and go from there now.... This will be my first level fifty here and I think it would be wise for me to make sure I get in high end pve raids to be able to get some templateable gear. I guess I can always respec later once I have accumulated some money.

Red spec buffs are not needed as long as you got red endu atleast you shouldn't have any problems in getting a pve grp.
In my opinion you should go for pbaoe disease and put atleast enough in mending to get the cure disease spell. You will not use the yellow ae dot in rvr because its usually the worst idea to use dot in rvr and give a cc free time to your enemies

8 Mend
46 Aug
27 Cave

Should work fine for PvE raids aswell. You'll only be missing red q/d but should be possible for people to live without that. Otherwise could you just tell them to charge