I work in a peds hem-onc-BMT clinic/day hospital but I thought I would pitch in anyway because we see the same population.
I can't help you with ratios since I'm outpatient and personally see anywhere from 3-16 patients a day depending on how intensive each one is (I have three rooms at any given time). We do anything from simply draw labs, to infusing chemo and blood products, to running fever-neutropenia/near-code cases. We access ports, CVCs, PICCs, and perform venipuncture every day. We do a little of everything, which is unique to outpatient but that's because we do, as you said, see the sickest patients.
No other population would be allowed to leave the hospital with the counts our kids have. When I transferred here from the emergency room I routinely panicked over lab results that the other nurses would barely glance at before replying "Oh that's normal for them" or even "Those look great! Their counts are really improving!"
Yes, they are some of the sickest patients, but most of the time you wouldn't know it. I've never taken care of a more inspiring population. Kids are so resilient and you don't see it better anywhere else. One pre-teen girl has so embraced her baldness: she has the largest collection of embellished headbands any of us have ever seen and she ROCKS a new one daily; she is so sassy, I love her! I have many pre-school age patients who handle their port accesses with amazing stoicism. And the families are amazing with their patience and overall outlook on life, even if they have already lost one or more children to the same disease.
Coming from PICU you are no doubt accustomed to bonding with patients and families and then experiencing their loss, but it will get worse if you move to hem-onc because you won't just know them for days or weeks or months but years. You will see them be declared disease-free just to see them come back a month or a year later, relapsed. You will sing and dance and celebrate with them when they go into remission even though you know the probability that it will not last. You will be them when they are diagnosed with things like DIPG which are literally death sentences -- no cure in sight -- and watch them decide to participate in trials that provide no hope for them but may one day give us a cure for someone else. You will repeatedly poke them to draw labs that are only for the benefit of others as they grow weaker and weaker. But it will be worth it because of who they are. Because they are the weakest and strongest people in the world.
So depending on why exactly PICU is no longer for you, hem-onc could be an excellent or horrible switch. I got burnt out in the ED from the constant rush and the feeling that I wasn't making the most of my time with the non-urgent cases that came through and only took my current position in hem-onc because it was the only one available but I have fallen in love with it. The people who tend to work hem-onc are also a special breed of caring loving and supportive nurses who treat their coworkers as well as they treat their patients.