It really depends, mono sents can make it in ELO if you can dodge SOA all day (SOB is not as big a problem for sents as it is for, say, montanas), half-deck sents without Lehane suffer pretty badly though.
For reference, my mono Sentinel build which I was able to take all the way to 1306 after falling from 1380 to 1187 is:
I'm using a sentinal half deck combined with Geist. It's working Ok so far, but I'm kinda a newb, so I don't know if it could be improved. It has some room, but I'm strapped for clintz.