Hey there,
The key here is to have a plan and stick to it. While it can be tempting to go overweight in a position, that is very much a risk proposition and should only be done if it fits within your risk profile. There is also more risk to going overweight in something like ATZ vs T as one is a growth stock and the only is one of the premier dividend growth stocks in the country - which means more volatility for ATZ, less for T.
All in all however, it is important that investors stick to their plant and allocations. If you have room in your allocations to add to get back up to an equal weight position - then it's not a bad idea to be adding here. Going overweight on any position is not really something I'd advocate for unless, of course, you have high conviction and a higher risk tolerance. For example, I typically try to keep our high growth exposure in stocks like ATZ and TIXT at less than 2% of our portfolio but for something like Telus, I am ok with going up to 5% - Dan is similar in that respect. That is however, in line with our risk tolerance.
Furthermore, personally, I like to let the dust settle for a bit after a big drop before adding. See how the markets react and may even give it a quarter or two and see how the company is doing. That may mean that I miss the "bottom" but I am always ok with missing the bottom if it means having a little more confidence in my decision to add. Once again, however, this is in line with my risk tolerance.
Mat