Is this the trend in some hospitals?

That is way too much in a step-down or CCU setting. Two or three pts max in step-down(with vents,not a regular tele floor.) You need to find a new job. You face the very real possbility of errors causing permenant damage or death, you will burn out, not to mention the possibility of losing your license. The institution is putting their pts and staff in danger.

Are the vents chronic trachs that are not unstable or difficult to manage ie Vencor type patients? The staffing ratio you describe sounds like an LTAC setting vs acute. And you also have fresh 2nd day CABG patients?? Personally I would not want this mix as you describe and I wouldn't renew my contract. Sounds dangerous to me.

All Stepdown patients units I've worked have been without vents. Some are going to chronic trachs waiting for LTC placement I hear.

This is why as a long time traveler (9 yrs now) I discuss all these things in my interview with the hospital: "What is your float policy?", "What units would I be expected to float to?" "What is the nurse/pt. ratio on each of these units?" If the answers are not comfortable to me, I refuse that contract. I make it clear that I am willing to float IN ROTATION with the regular staff, will take patient assignments only on those units I am experienced in, and if floated to other units will task only as I feel pt. safety is compromised if I don't have the skills to assess their condition. If this is not satisfactory to the manager, again I don't take that assignment. My company/recruiter is also aware of these stipulations, so no surprises for them either.
When the situation occured that I was pressured after already on an assignment to change this, my company fully supported me in leaving that assignment.
The bottom line is, there are plenty of assignments out there, don't accept one that makes you feel your job or license are on the line.

For ICU the worst I've had is 2 vent patients. Most 1:1's I've seen have been CRRT or balloon pumps. For stepdown, I've had up to 6 patients, no vents, post cath, active chest pain, vasoactive drips, etc.