First of all, the fastViewOption will only have an effect if RTSF output is turned on for the simulation (and that will only do anything if the output format is psfbin or psfxl). Secondly, it only helps for signals directly plotted in the waveform tool, and if you build a signal and plot it using plot(), you will most likely not get the speed benefit. That's because it has to load in the entire waveform, and the optimisation is lost.
psfxl output format should help significantly in terms of data load time, so use that if you can (this is the default from IC615 ISR4 onwards).
And IC615 will help in terms of load and draw performance anyway because in IC614 the graph is a separate (Java) process, and so the data is loaded into the ocean/virtuoso process, and then may be sent across to the java process using IPC; in IC615 it is a single process using Qt graphics, and so there's no IPC needed. The graphics performance should (in general) be better.
If after doing this you still have performance issues, please contact customer support - this is something that has had a lot of focus on, especially in IC615.