again...as an old tower controller I would NEVER have cleared the succeeding aircraft for takeoff until I was SURE the previous departing aircraft was 6000 ft+ and AIRBORNE... pilot wasn't watching...controller wasn't watching...

old tower controller too... I was taught never to anticipate or "bet on the come"..

Help is on the way——

On Saturday, new Federal Aviation Administration rules about pilot rest took effect in America. The rules, which airlines were warned about two years ago, require that pilots have 10 hours of rest, including eight hours of uninterrupted sleep, in between their eight- or nine-hour shifts. That's up from eight hours of rest before—which didn't have to include uninterrupted sleep. The changes were prompted, in part, by the 2009 crash of Colgan Air Flight 3407.
https://www.economist.com/gulliver/2014/01/07/preventing-sleepy-pilots

Canadian Rest Rules (Dec 2018 article)
Transport Canada has cut maximum on-duty periods for pilots and tweaked pilot rest requirements in a move regulators describe as more-closely aligning Canadian rules with international standards.
When the new rule takes effect in two years for large airlines, duty days will capped at between 9h and 13h depending on factors like flight duration, the number of daily flights flown and duty start times.
A pilot scheduled to fly seven daily flights starting at midnight, for instance, will be limited to a 9h duty day, while a pilot flying four daily flights starting at 08:00 can be on duty for 13h, the rules say.
Transport Canada issued the new regulations on 12 December 2018 more than four years after formally proposing changes.
The new rule also trims annual flight time limits to 1,000h, down from 1,200h, and the limit is now 112h in 28 days, down from 120h in 30 days.
Transport Canada also tweaked rest period requirements, which were formerly set at 8h (plus time for meals, hygiene and travel) between duty periods. Now, pilots must have 10h rest in "suitable accommodation" when away from their home base, or, when at their home base, up to 12h.
The rule does, however, allow airlines with "unique operations" the flexibility to operate outside prescribed limits if they develop a "fatigue risk management system".
https://www.flightglobal.com/safety/canada-cuts-pilot-duty-times-and-extends-required-rest-periods/130674.article

The new fatigue rules will limit pilots to 1,000 flight hours in any 365 consecutive days, compared with the 1,200-hour limit in current regulations. The new regulations will retain the existing 300-hour limit for 90 days and add a new requirement of no more than 112 flight hours in any 28 consecutive days. Currently, pilots may fly no more than 120 hours in any 30 consecutive days. The new regulations will eliminate the existing requirement of no more than 40 to 60 hours in any seven consecutive days.
The new regulations will set a maximum flight duty period of between nine and 13 hours, depending on starting time and sectors flown. The previous limit was about 14 hours.
The fatigue rules also will extend required rest periods from approximately eight hours under current rules to between 10 and 12 hours under the new rules. https://flightsafety.org/new-fatigue-rules/

Sorry but I disagree about Air Canada following the rules. I know 5 flight crew members who worked over the eloted time. Not much was done about it. So yes, they are lackadasical.