You can only use so many attacks though. Blasters tend to have too many available. That's where scrappers builds tend to be designed around.
If you have scrapper level survival, you are going to end up with Scrapper level damage, adjusted for range. Not that Range matters a lot as far as doing damage usually. Some opportunity based stuff.
But I don't think Sentinels are there yet, are they?
This is just my rough feel on where you could take it though. I don't see Capt PH saying Sents can do equal damage to a Ranged (primary attacks) only Blaster both ST and AOE.